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  • International Union of Crystallography (IUCr)
  • 1990-1994
  • 1980-1984  (2,141)
  • 1983  (1,137)
  • 1981  (1,004)
Collection
Publisher
Years
  • 1990-1994
  • 1980-1984  (2,141)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Design criteria for a laboratory EXAFS facility (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 3-7 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: There has recently been an increased amount of interest in laboratory equipment for extended X-ray absorption fine-structure (EXAFS) measurements. In an earlier paper a facility for performing such measurements easily in a few hours was described in some detail. In this paper, further development of the techniques is reported. The use of high-power rotating-anode X-ray generator, the design of an X-ray curved-crystal spectrometer, the factors governing the proper choice of monochromator crystals and the design of fast-counting detectors and electronics are discussed. In addition, it is shown how errors caused by characteristic lines in the spectrum can be eliminated by use of a flux stabilization circuit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008571
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron photographic measurements of protein single-crystal reflections (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 24-27 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Photographic neutron intensity measurements on a 2 mm3 single-crystal of triclinic lysozyme are compared with conventional neutron diffractometer data. The reflections were recorded with the oscillation technique. The structure factors were derived from the optical densities scanned by an automatic microdensitometer and processed by computer programs. A statistical analysis shows that the photographic data are of about the same accuracy as recently collected diffractometer data. For the same flux and crystal volume the data collection time is reduced by up to two orders of magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008601
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  • 3
    Electronic Resource
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    A device for accurate single-crystal X-ray diffraction investigations at non-ambient temperatures: 83–1120 K (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 43-50 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A device is described which uses liquid nitrogen to generate a cold or hot gas stream which is blown directly onto the crystal mounted on an X-ray diffractometer. With a specially constructed high-vacuum (〈 1.3 × 10–5 Pa) jacketed silica Dewar tube, it can operate between 83 and 1120 K with a stability over long time periods of ± ¼ K below and ± 1 K above ambient temperature. In the latter case the short-time stability is ± ¼ K for hours. It gives an inert atmosphere at elevated temperatures and allows extensive data collection for the accurate determination of crystal structures. The evaporator, the automatic refilling system and the silica Dewar tube are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008649
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  • 4
    Electronic Resource
    Electronic Resource
    A fitting method for X-ray diffraction profiles (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 60-61 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A fitting method is proposed for X-ray diffraction profiles which requires only a small number of parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008686
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  • 5
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    Crystal data for two series of solid solutions: (RbxK1−x)MgCr2(VO4)3 and (TlxK1−x)MgCr2(VO4)3 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 61-62 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Complete solid solution is observed amongst the compounds of the type M1MgCr2(VO4)3 (where M1 = K, Rb or Tl). The solid-solution series obtained show linear changes in peak positions and peak intensities in their X-ray diffraction patterns. The crystallographic behaviour with respect to the value of x for (RbxK1−xMgCr2(VO4)3 and (TlxK1−x)MgCr2(VO4)3 solid solutions is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008698
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  • 6
    Electronic Resource
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    Crystal data for ferric molybdate: Fe2(MoO4)3 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 64-65 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Indexed powder patterns of the monoclinic phase, stable at room temperature, and of the orthorhombic phase, stable for T 〉 786 K, are given. The cell dimensions are: a = 15.737 (8), b = 9.231 (5), c = 18.224 (9) Å, β = 125.46 (2)° at 295 K; a = 9.330 (3), b = 12.868 (5), c = 9.242 (3) Å at 818.6 K. Linear equations describing the thermal expansion of the two phases of ferric molybdate are reported. To verify if ferric molybdate can incorporate excess MoO3, measurements on non-stoichiometric samples were also made: no evidence of the presence of excess MoO3 was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008716
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  • 7
    Electronic Resource
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    Crystal data for high-temperature As2O5 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 68-68 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: High-temperature As2O5 at 768 ± 5 K is tetragonal with a = 8.577 (1), c = 4.637 (1) Å, V = 341.2 Å3, Z = 4, Dc = 4.475 Mg m−3. Indexed powder data are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988100873X
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  • 8
    Electronic Resource
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    Characteristics of a flat multiwire area detector for protein crystallography (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 85-93 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A flat, relatively thin (9 mm) xenon-filled multiwire proportional counter with two-dimensional, 2 μs delay line readout of a 270 × 300 mm active area has been developed for use as a position-sensitive area X-ray detector in the 8 keV energy region (Cu Kα) used in crystallographic structure work with large biological molecules. Its quantum detection efficiency for 8 keV X-ray photons is about 0.5, a value which is spatially uniform to within ± 2%. Its dead-time loss fraction at a typical data collection rate of 30000 photons s−1 is 12%. The detector has spatial resolution for X-rays of 0.6 mm FWHM in the horizontal direction and 2 mm, the anode wire spacing, in the vertical direction. The effects of parallax are found to be limited and do not seriously increase the apparent size of the diffracted beams. The position sensitivity of this detector is geometrically linear to within 0.5 mm across its active surface. Routine maintenance of the detector requires the attention of a skilled technician but is not time consuming. For four years, this detector has been used to measure millions of reflection intensities from crystals of many different proteins. The down time due to the detector has averaged less than four days per year, considerably less than the down time of other components of the data collection system. Four new protein structures have now been solved using data from this detector. Also, a considerable amount of data have been collected at higher resolution or at different temperatures with crystals of other proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008856
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  • 9
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    An assessment of instrumental parameters which control the accuracy of stress measurement using the X-ray diffractometer method (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 124-130 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The sources of systematic error in the X-ray diffractometer method of stress measurement are discussed. The errors in stress measurement and correction procedures for their elimination are described and quantitatively assessed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988100890X
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  • 10
    Electronic Resource
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    The use of cell and symmetry information for single-crystal orientation on diffractometers (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 117-123 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The diffraction aspect and rough cell parameters of a crystal to be studied are usually known before mounting the crystal on a diffractometer. Such data are used for orientation purposes in the method described. An ordered list of indexed 2θ values is calculated from which an optimum 2θ for a peak search is derived. The peaks found are centered, their possible unique indices are derived by comparison of the observed 2θ values with the calculated values. Two intense reflections with few indexing ambiguities are selected to define the crystal orientation. Their possible pairs of indices are found by considering combinations of indices related to the unique indices by the Laue-group symmetry and for which the calculated angle between the reciprocal vectors is comparable with the observed angle. Only the non-equivalent orientations defined by these initial pairs will be accepted. An initial pair will be rejected if the indices of both reflections can be transformed into those of a previously accepted pair by a single Laue-group symmetry operator of the first kind. The correct setting is usually obvious from a very short list of possible orientations and is retained. This simple approach has been programmed and treats all symmetries without branching of the logic. Rhombohedral crystals can be referred to hR or rP cells. The possible non-equivalent settings due to metric ambiguities, to pseudo-symmetry or to symmetry are exhaustively listed, but no symmetry-related setting is indicated. This scheme has automatically oriented more than 40 crystals from the seven crystal systems in 20–50 min each. The wavelength, the cell parameters and the short symbol of a valid space group in the correct diffraction aspect are the only input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008893
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  • 11
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    Neutron powder diffraction of forsterite, Mg2SiO4: a comparison with single-crystal investigations (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 137-139 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Neutron time-of-flight powder data have been collected for forsterite [Mg2SiO4; Pbnm (D162h, No. 62); Z = 4, a = 4.7534 (1), b = 10.1989 (2), c = 5.9813 (1) Å] with the ZING-P′ high-resolution diffractometer at Argonne National Laboratory. Forty-seven variables, including anisotropic temperature-factor coefficients, were refined with a profile-fitting procedure to R(profile) = 2.10% and R(Rietveld) = 3.53%. Positional and thermal parameters are in good agreement with those determined from recent X-ray and neutron single-crystal diffraction experiments. Results suggest that powder data can be used to obtain accurate positional parameters and reasonable temperature factors for moderately complex structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008935
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  • 12
    Electronic Resource
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    Adaptation of a Kratky camera to use with a one-dimensional position-sensitive detector (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 139-141 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A Kratky small-angle X-ray camera was modified so as to allow the use of a one-dimensional (one-dimensional) position-sensitive detector (PSD) with it. The modification was designed in such a way that most of the calibrations, necessary for subsequent correction of the collected intensity data, can be performed with little alteration in the collimation geometry or the electronics settings. In particular, the calibration of the uniformity of detector efficiency can be performed by repeated vertical travel of the detector at a constant speed across a beam scattered from a sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008947
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  • 13
    Electronic Resource
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    XPKFIT: peak separation with arbitrary relations among the component peaks (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 145-148 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A computer program for the separation of a composite peak into the components and the background has been written in Fortran. Each component is approximated by a function of the form y(x) = c [1 + ({{x - d}\over{e}})^{2}]^{-f}, where c, d, e and f are the parameters to be determined by a least-squares method. Arbitrary, known or assumed relations among the parameters of different components may be read in to reduce the number of independent parameters and save computation time or, in other cases, to offer a better chance of separating a complex composite peak by varying a subset of the parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881008984
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  • 14
    Electronic Resource
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    BLOKJE, a computer program to calculate the domain of an atom in a structure (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 151-153 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A computer program has been written with the aim of calculating the domain of an atom in a structure. The domain may be limited by planes situated half-way between the atoms, or at a distance that takes into account the relative radii of the atoms. Data concerning this domain and the corresponding coordination polyhedron are computed and printed. Punched cards, to be used in a special plotting program, can also be produced. Three types of weighted coordination number are calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988100900X
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  • 15
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    The use of continuous diffraction data as a phase constraint. I. One-dimensional theory (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 160-168 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Intensity can often be measured as a continuous function of scattering angle in diffraction from non-crystalline specimens. An analysis of the amount of information contained in one-dimensional continuous diffraction data is presented here. This analysis, based on the sampling theorem and the theory of entire functions, indicates that there is a limited but often rather large number of possible phase solutions to any given continuous intensity distribution. A refinement technique has been developed which allows phase solutions to be found that are consistent with the diffraction data and with other physical and chemical data. In favourable cases, when diffraction data is used in coordination with other kinds of data, there can be enough information in a diffraction pattern to identify a unique structural solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881009060
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  • 16
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    The small-angle neutron scattering spectrometer at the University of Missouri research reactor (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 370-382 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A small-angle neutron scattering (SANS) spectrometer has been constructed at the University of Missouri Research Reactor Facility (MURR). The design of the MURR–SANS is unusual in that the size of the reactor containment building constrains the flight path to be vertical. This is achieved by Bragg scattering upward through 90° from a set of slightly misaligned pyrolytic graphite crystals to provide a neutron beam at 4.75 Å with a wavelength spread of approximately 4.1%. The beam incident on the sample is defined by two matched variable apertures located either 3.0 or 4.5 m apart. The evacuated scattered flight path is designed with removable extensions to match the primary flight path in length. The instrument has an automatic sample handling capability provided by its own dedicated PDP 11/03 computer. The detector is a large assembly of commercially available linear 3He detectors as an economic alternative to a crossed-wire two-dimensional multi-detector. An array of 43 position-sensitive proportional counters, 24 in (609.6 mm) long and 0.5 in (12.7 mm) in diameter, using charge division gives a spatial resolution of 5 x 12.7 mm. The area-averaged detector efficiency is about 84% at a wavelength of 4.75 Å. The range of scattering vectors that can be measured is 0.005 〈 Q〈 0.15 Å−1. The instrument is well suited to a wide variety of experiments on specimens having characteristic dimensions between 20 and 500 Å. MURR–SANS is designed as a user-oriented facility which provides both reasonable resolution and intensity on sample at a modest cost, and forms part of a neutron scattering center.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889881009631
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  • 17
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    A study of the ordered structures of the Au–Mn system by high-voltage–high-resolution electron microscopy. II. Two-dimensional antiphase structures based on the DO22 structure (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 392-400 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Two-dimensional antiphase domain structures existing in the composition range 20–23 at.% Mn were investigated by a high-resolution structure-imaging technique with a 1 MV electron microscope. The structures are based on the DO22 structure and consist of parallelogram-shaped domains containing 4 × 3 columns of Mn atoms and lozenge-shaped domains with 4 × 4 and 3 × 3 columns, and the domains are separated by two-dimensional antiphase boundaries parallel to the ({\bar 2}40) and (240) planes of the fundamental face-centred structure. The configuration of the domains changes delicately with a slight change of composition or annealing temperature, and the symmetry of the structure is lowered below about 670 K. The ideal structure models have compositions of about 22.7 at.% Mn. The images of about half of the specimen area of the 22.6 at.% Mn alloy annealed at 570 K do not correspond to these new structures, but bear a resemblance to the image expected from the two-dimensional antiphase structure proposed by Watanabe [J. Phys. Soc. Jpn (1960), 15, 1030–1040] for Au3Mn, which is based on the L12 structure and has boundaries parallel to the (100) and (010) planes.
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    URL: http://dx.doi.org/10.1107/S0021889881009667
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  • 18
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    Comparison of two numerical methods for the integration of the Takagi–Taupin equations (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 432-436 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Two methods for the numerical resolution of the Takagi-Taupin equations are compared. It is shown that for a small integration step Taupin's [Acta Cryst. (1967), 23, 25–35] extension to two dimensions of the one-dimensional Runge–Kutta third-order method is more accurate than the algorithm of Authier, Malgrange & Tournarie [Acta Cryst. (1968), A24, 126–136] but, for a given precision, Authier, Malgrange & Tournarie's method is faster than Taupin's so the former will usually be preferred for numerical calculation.
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    URL: http://dx.doi.org/10.1107/S0021889881009709
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  • 19
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    Dependence of cooling rate of SAXS spectra from a B2O3–PbO–Al2O3 glass (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 444-446 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The phase separation of an 80% B2O3–15% PbO–5% Al2O3 (weight %) glass after splat-cooling was studied by small-angle X-ray scattering. The wavenumber which receives maximal amplification and the scattering intensity corresponding to this wavenumber were determined as a function of the cooling rate of the glass. The experimental results qualitatively agree with the main features of previous calculations based on the linear theory of spinodal decomposition, but no quantitative agreement is obtained.
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    URL: http://dx.doi.org/10.1107/S0021889881009734
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  • 20
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    Phase assignment to diffraction patterns based on the analytic properties of scattered fields applied to the structure of nerve myelin (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 455-461 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An analysis of published X-ray diffraction data from nerve myelin is given based on the properties of analytic functions. Functions defined by a finite Fourier transform may be described by their distribution of zeros. This description allows a phase function to be determined from real data, which is unique in principle. A solution to the phase assignment is given and compared with corresponding published solutions derived by other methods. The strong measure of agreement for the phases of the first nine diffraction orders, and the stability of this agreement against the efforts of experimental error, leads to the conclusion that these phases are probably correct.
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    URL: http://dx.doi.org/10.1107/S002188988100976X
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  • 21
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    Crystal data for [2.1.2.1]paracyclophan C30H28 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 465-465 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The powder data for [2.1.2.1]paracyclophan is reported. This compound is monoclinic with a = 21.44 (4), b = 17.22 (6), c = 9.70 (4) Å, γ = 141.30 (3)°, Z = 4.
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    URL: http://dx.doi.org/10.1107/S0021889881009795
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  • 22
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    Report of Executive Committee for 1980 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 491-491 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988100993X
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  • 23
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    A simple procedure for fitting a backgound to a certain class of measured spectra (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 226-229 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A numerical procedure using orthogonal polynomials is used for extracting the background in measured spectra. An X-ray spectrum obtained with the energy-dispersive method is considered as an example.
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    URL: http://dx.doi.org/10.1107/S0021889881009242
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  • 24
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    X-ray measurement of the static Debye–Waller factor of NbHx (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 251-256 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Integrated X-ray Bragg intensities from Nb single crystals have been measured as a function of H concentration and scattering vector along high-symmetry directions. The observed attenuation can be described in terms of a static Debye–Waller factor (DWF) due to the static displacements of the Nb lattice atoms around the dissolved H. The crystals were loaded with H in situ on the X-ray diffractometer. The static DWF was determined from the ratio of the intensities from a crystal with and without H. Corrections are necessary for several magnitudes which change with the lattice-parameter change and the change of the thermal displacements upon the uptake of H. The measured static DWF is proportional to the H concentration c(H/Nb) for c≤0.30 and the square of the scattering vector K2 for small K, as expected from theory. From analysis of the static DWF the static displacements of the Nb atoms closest to the H impurity u1 = 0.1 Å were determined.
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    URL: http://dx.doi.org/10.1107/S0021889883010328
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  • 25
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    Crystal data for 2-(4-methyl-2-pyridyliminomethyl)phenol and 2-(4,6-dimethyl-2-pyridyliminomethyl)phenol (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 276-276 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Crystal data for the Schiff bases 2-(4-methyl-2-pyridinyliminomethyl)phenol (salampy) and 2-(4,6-dimethyl-2-pyridyliminomethyl)phenol (saladimpy) are reported. Salampy: C13H12N2O, Mr = 212.0, P21/c, a = 11.772(4), b = 7.5386(7), c = 15.154(5) Å, β = 124.89 (2)°, V = 1103.1(4) Å3, Dm = 1.24, Dx = 1.28 g cm−3, Z = 4; saladimpy: C14H14N2O, Mr = 226.0, P212121, a = 21.585(5), b = 8.8285(8), c = 6.2952(6) Å, V = 1199.6(3) Å3 Dm = 1.22, Dx = 1.25 g cm−3, Z = 4. The JCPDS Diffraction File No. for C13H12N2O is 33-1999, for C14H14N2O 33-1998.
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    Crystal data for bis(η5-tert-butylcyclopentadienyl)hafnium(IV) dihydride dimer, [(η5-t-BuC5H4)2HfH(μ-H)]2 (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 277-277 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The air-sensitive title hydride [Hf(C9H13)2H2]2 was prepared by hydrogenolysis of (t-BuCp)2HfMe2 [Couturier, Tainturier & Gautheron (1980). J. Organomet. Chem. 195, 291–306] and crystallized from a solution in heptane or toluene and hexane. The compound is triclinic with the following cell parameters: a = 7.22(3), b = 10.31(4), c = 12.47(6) Å, α = 80.4(4), β = 74.6(4)°, γ = 72.1(3)°, V = 847 Å3, Z = 1, Dx = 1.67 Mg m− 3. Powder diffraction data were obtained from Debye–Scherrer photographs. The extended version of the paper examines several examples where Zr or Hf hydrides are monomers or dimers and shows that this structure is very similar to the related [(MeCp)2ZrH2]2 compound [Jones & Petersen (1981). Inorg. Chem. 20, 2889–2894]. This similarity and spectroscopic data show that the molecule probably has a center of symmetry situated between the two Hf atoms and the two bridging H atoms. The JCPDS Diffraction File No. for [Hf(C9H13)2H2]2 is 33-1996.
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    International Tables for Crystallography (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 284-284 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    On the X-ray reflectivity of elastically bent perfect crystals (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 295-303 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: The integrated X-ray reflectivity of elastically bent, but otherwise perfect, crystals are calculated for Laue-type reflections covering the entire curvature range. Anomalous transmission and elastic anisotropy are taken into account, and it is shown that both these effects affect appreciably the reflected intensities for both weakly and strongly bent crystals. The validity of the reflectivity-versus-curvature relation thus obtained is experimentally confirmed for a number of reflections from silicon crystals. The implications of the experimental results to brittle fracture are discussed.
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    Use of high-symmetry zone axes in electron diffraction in determining crystal point and space groups (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 317-324 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A sequence of steps is given for making use of the information available on convergent-beam electron diffraction patterns from high-symmetry zone axes for crystal point- and space-group determination.
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    Observations on the phase transition in quartz by synchrotron-radiation X-ray topography (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 354-356 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: By use of a high-temperature camera designed for in situ synchrotron-radiation X-ray topography the α−β transition was investigated in a Z-cut synthetic-quartz sample. Preliminary dynamical observations on movement of the boundaries between α and β phases and α1 and α2 domains are reported.
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    The crystal structure of α-mercury(II) peroxide (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 357-357 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The crystal structure of α-HgO2 was determined using X-ray powder diffraction. The crystal is C-centered monoclinic, C2/m, a = 4.470(2), b = 5.459(2), c = 3.519(2) Å, β = 108.45°, Z = 2, Dx = 9.48 g cm− 3. The variable coordinates of oxygen atoms from the peroxide dumbbell were determined as x = 0.476, z = 0.280. The final R is 0.047. The JCPDS Diffraction File No. for α-HgO2 is 33-1489.
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    PROMETHEUS. A program system for investigation of anharmonic thermal vibrations in crystals (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 358-358 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: PROMETHEUS is a Fortran IV program system for investigation of anharmonic thermal vibrations in crystals, using elastic X-ray or neutron data. Three different anharmonic temperature-factor equations can be used, one of them up to sixth-order terms. The corresponding probability densities and mean effective atomic potentials can be calculated. Programs for correction of isotropic thermal diffuse scattering and of isotropic and anisotropic extinction are included. Fast averaging of symmetrically equivalent reflections combined with extended reflection statistics is possible. Calculations of Fourier syntheses and their errors and of Patterson functions can be carried out and the corresponding contour maps can be plotted.
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    The effect of finite detector slit height on peak positions and shapes in powder diffraction (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 508-511 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The finite height of the detector slit of a powder diffractometer has three observable effects: (1) the peak is shifted by an amount that is proportional to −cot 2θ; (2) the peak is broadened by an amount proportional to cot22θ; (3) an asymmetry is introduced into the peak shape that depends on cot32θ. If the underlying instrumental resolution function has a Gaussian shape, the slit height effects can be approximated, over a rather broad range of shapes for the vertical resolution function, by an Edgeworth series making use of one adjustable parameter. This peak shape function is compared with experimental observations and with other shape functions that have been proposed. A well characterized peak shape is at least as important as resolution when the data are to be used for structure refinement by the Rietveld technique, and diffractometers should be designed so as to keep the slit height within the range that leads to shapes that can be described mathematically. Diffractometers with multiple detectors can usefully have different vertical divergences for detectors that cover different angular ranges.
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    A method for collection of step-scan data on a CAD4 diffractometer, homogeneity of the monochromated primary X-ray beam (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 11-13 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A procedure for collecting protein data by a simulated step-scan method is described for a CAD4 diffractometer. The method allows one to collect 100–150 reflections per hour without any significant loss in accuracy, thus reducing the time spent on each reflection by a factor of 2–3 compared with the ω–2θ scan technique. A comparison between data collected for the protein phospholipase C by the present method and by the ω–2θ technique gives a reliability factor of 2%. Prior to this work the homogeneity of the X-ray beam from a graphite monochromator was determined, and the intensity cross section of the monochromatized X-ray beam showed that the total X-ray illumination of the crystal is practically unchanged regardless of the orientation of the crystal in the primary beam.
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    A computer program generating parameters useful in X-ray diffraction topography studies (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 577-578 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A simple Fortran computer program XRTDAT is described. This program generates data useful in the planning, execution and interpretation of an X-ray topographic experiment.
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    Industrial crystallization 81 edited by S. J. Jancic and E. J. de Jong (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 580-580 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    The sampling theorem and small-angle scattering (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 581-589 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: All information about the scattering sample obtainable from small-angle scattering data is shown to be contained in the discrete measured points of a scattering curve distorted by arbitrary collimation conditions, provided that the interval Δh between adjacent measured points fulfils the condition Δh ≤ π/L, where L is the largest correlation distance in the sample; h = 4πλ−1sinθ; λ is the scattered wavelength; and 2θ is the scattering angle. A simple technique has been developed for separation of part of the noise. It is shown that if the total time for measuring a scattering curve is held constant, a scattering curve recorded with Δh equal to the sampling-point interval π/L gives results like those obtained for a scattering curve recorded with a measured point distance smaller than that sampling-point interval. Therefore, Δh should be chosen to be small enough to guarantee that Δh ≤ π/L. Furthermore, a technique has been developed to calculate missing data points from the measured intensities. The condition Δh ≤ π/L has been found to be important for this calculation.
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    Crystal-structure refinement by profile fitting and least-squares analysis of powder diffractometer data (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 611-622 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: The refinement of crystal structures using X-ray powder data in a two-stage method is described. (1) The integrated intensities of the individual reflections are derived by a profile fitting method in which the profile shapes are accurately defined using an experimentally determined instrument function and the sum of Lorentzian curves. (2) These values are then used in a powder least-squares refinement for structure determination. The results obtained with three simple structures (silicon, quartz and corundum) gave R(Bragg) values of 0.7 to 2.5%. The necessity of correcting for preferred orientation and the importance of proper specimen preparation are also discussed.
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    Lattice-parameter measurements of PbHPO4 single crystals by the ratio method (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 623-628 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Temperature dependences of PbHPO4 single-crystal lattice parameters were measured by the ratio method in the range 158–421 K. Below the ferroelectric phase transition (Tc = 310 K) lattice parameter b increases non-linearly with decreasing temperature while all others decrease linearly. The ratio method was generalized to the monoclinic crystal system for this purpose.
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    Correction for escape in X-ray spectra measured using a Ge detector (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 641-644 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: X-ray spectra measured with a germanium detector can be corrected for escape. A numerical procedure to perform the correction has been implemented. The method employs a point by point subtraction and allows for energy-dependent detector resolution.
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    Asymmetrically grooved monolithic crystal monochromators for suppression of harmonics in synchrotron X-radiation: erratum (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 648-648 
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    Notes: A typographical error has occurred in Hashizume [J. Appl. Cryst. (1983). 16, 420–427]. The first two complete sentences on page 425 should read: A attains a minimum value of 0.024 at bII = 0.27, where about half of the initial fundamental intensity is preserved. The initial rise of the fundamental intensity, which occurs in the range 1.0 〉 bII ≥ 0.64, is accounted for by a close examination of the overlap pattern of R(1)HI and, R(1)0II at the relevant bII values: the shifted and extended peak profile of R(1)0II admits the high-angle tail of R(1)HI and rejects the low-angle flank of R(1)HI, and the gain due to the former more than compensates for the loss caused by the latter.
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    Diagrammes de poudres de l'iminostilbene, C14H11N, de l'iminodibenzyle, C14H13N, et de son derivé: le chloro-3 iminodibenzyle, C14H12ClN (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 649-649 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: X-ray powder data have been obtained for the three title compounds, fundamental members of a group of psychotropic drugs. For the first two compounds, the crystal structures of which have previously been solved [Reboul, Cristau, Soyfer & Estienne (1980). Acta Cryst. B36, 2683–2688; Reboul, Cristau, Estienne & Astier, (1980). Acta Cryst. B36, 2108–2112], the powder patterns were indexed on the basis of an orthorhombic unit cell with the lattice constants a = 8.22 (1), b = 20.40 (1), c = 6.03 (1) Å, space group Pnma for C14H11N; C14H13N is monoclinic, space group P21/c with a = 11.60 (1), b = 11.27 (1), c = 20.05 (1) Å, and β = 126.5 (1)°. C14H12ClN is also monoclinic, P21 or P21/m, with Z = 2, a = 11.68 (1), b = 8.08 (1), c = 12.13 (1) Å and β = 95.6 (1)°. The JCPDS Diffraction File Nos. for these compounds are: C14H11N 34-1995; C14H13N 34-1996, C14H12ClN 34-1994.
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    Measurement of the atomic coordinates of a Kendrew-type model from two projections (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 658-659 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    A computer program for the deconvolution of X-ray diffraction profiles with the composite of Pearson type VII functions (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 653-657 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A computer program for the deconvolution of X-ray diffraction profiles has been written in Fortran IV. The deconvolution procedure is based on the minimization of the difference between the observed data function and a calculated function, where the latter is the convolution of the instrumental function and the true data function approximated with an analytical expression. The composite of two asymmetric Pearson type VII functions was assumed to represent the true data function, and the simplex method was used for the minimization. The stability of convergence and the influences of the truncation effect and the step width of intensity data on the deconvoluted profile were examined. The computer program can deconvolute the X-ray diffraction profile in moderate computation time without generating spurious oscillations due to the truncation effect.
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    Refraction corrections to the diffractometer angles of centered reflections from extended-face single crystals (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 247-252 
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    Notes: The effect of refraction on the observed diffractometer angles θr, ωr and χr of a centered reflection is discussed for general asymmetric reflection from a finitely absorbing extended-face crystal. Formulae are presented for θr, ωr and χr for symmetric reflection and for θr and ωr for the two extreme positions of asymmetric reflection in terms of the angles calculated assuming that refraction can be neglected.
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    Complete determination of subgrain misorientation by an X-ray topographic method (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 265-269 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A modification of the Berg-Barrett X-ray topographic method was developed which enables measurement of all three misorientation parameters of a general subgrain boundary. The described method is based on the evaluation of three topographs of a single, arbitrarily oriented crystal surface taken by symmetric zero-layer reflections. In practical tests performed on an as-grown Fe–3 Wt% Si single crystal, relative accuracy of 10% and angular sensitivity better than 1′ were achieved.
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    An interactive graphics system for comparing the model building of macromolecules (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 274-279 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: An interactive graphics program is described for use with the Evans & Sutherland Picture System 2 which is suitable for the comparison and refinement of protein structures. Several protein molecules and electron density maps can be viewed simultaneously, while great flexibility exists in creating, modifying and manipulating the picture on the screen. As the program is file oriented, it can be run on a small computer system with only 32 K memory.
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    Anomalous thermal expansion of silver gallium telluride (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 281-284 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A precise X-ray determination of the lattice parameters of silver gallium telluride, AgGaTe2, has been made in the temperature range 301 to 667 K with a Unicam 190 mm high-temperature powder camera. The data have been used to evaluate the coefficients of thermal expansion, α⊥ and α\parallel, at various temperatures. It has been observed that the `c' parameter decreases while the `a' parameter increases with increasing temperature as in the case of AgGaSe2 and AgGaS2, which also have a chalcopyrite-type structure. The magnitudes of both α⊥ and α\parallel increase non-linearly with increasing temperature.
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    X-ray extinction contrast in deformed single crystals (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 285-290 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Berg–Barrett topography gives information on large-scale dislocation distribution in deformed single crystals. The Burgers vectors are determined by disappearance of the dark `extinction contrast'. This contrast cannot be extinguished by any single diffracting condition when different types of non-coplanar Burgers vectors are present simultaneously; complementary information by electron transmission microscopy agrees well with this inference. These general remarks are illustrated by some examples on deformed single crystals of α-Al2O3, (Al2O3)1.8MgO, NaCl and Cu2O.
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    Diffraction by layer structures containing different kinds of layers and stacking faults (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 300-304 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A description is given of a mathematical formalism which allows the study of diffraction by stacks which contain, simultaneously or not, (i) layers of different kinds, (ii) different translations or rotations between layers and (iii) different thicknesses. The formalism allows the calculation of intensities for all the hkl reflections or (h,k) reciprocal rods, and not just the 00l reflections. It accounts for an Sth-neighbour interaction (S≥1).
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    A pilot study of the use and unfocused monochromatic radiation from a storage ring in powder diffraction (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 315-320 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The results of a trial powder diffraction experiment on the ADONE storage ring at the Frascati National Laboratories (Italy) are described. A (220) channel-cut Si crystal was used to provide a monochromatic beam and it was demonstrated that Debye–Scherrer photographs could be obtained in several hours. It was also shown that very high resolution can be obtained simply by increasing the camera dimensions. Finally, it is shown that with the higher fluxes of the SRS at the Daresbury Laboratory (England) very fast exposures will be possible without the need for focusing.
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    Modulated structure of iron–carbon martensite studied by electron microscopy and diffraction (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 329-336 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Satellite spots appear around every fundamental spot in electron diffraction patterns of iron-carbon martensite (α′) tempered in a temperature range from 273 to 363 K. High-resolution electron microscopic observations show that they are due to the formation of a modulated structure, in which interstitial carbon atom clusters smaller than 10 Å are distributed randomly in a plane nearly parallel to (102)α′, with inter-cluster distance of 10–20 Å and such carbon-rich planar regions are spaced periodically with intervals of 10–20 Å, depending on the carbon content of the martensite. A structure analysis was made by measuring the satellite spot intensity of the electron diffraction patterns, and the displacements of atoms from their average positions in martensite were determined. The result supports the above cluster model for the modulated structure.
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    Crystal data for the double oxides MSbO4 (M=Cr, Fe) (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 348-349 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: MSbO4, (M = Cr, Fe) are tetragonal, rutile-type compounds, P42/mnm (No. 136); Z = 1. M and Sb are randomly distributed in 2(a) positions and O in 4(f). For CrSbO4, Dm = 5.31, Dx = 5.35 Mg m−1, a = 4.5899 (2), c = 3.0525 (2) Å, U = 64.307 (8) Å3, x = 0.318, R = 4.6; Cr and Sb are coordinated with two O atoms at 2.064 and four O atoms at 1.930 Å.
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    The fabrication of a dual-element X-ray divergent-beam target (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 352-353 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    World Directory of Crystallographers, Sixth Edition (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 354-354 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Laser crystals edited by A. A. Kaminskii (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 355-356 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    Crystal data for the oxidation product of bis(2,2'-bipyridyl)copper(I) perchlorate in nitroalkanes (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 475-477 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Single crystals of [Cu(bpy)2NO2]ClO4, [Cu(C10H8N2)2NO2]ClO4, C20H16CuN5O2.ClO4, with space group P21/c, were grown from the reacting mixture of bis(2,2′-bipyridyl)copper(I) perchlorate with molecular oxygen in nitroalkanes. The unit-cell parameters are a = 10.83 (2), b = 12.51 (1), c = 17.04 (1) Å, β = 112.0 (2)°, Z = 4, Dm = 1.62 (1) Mg m−3.
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    Crystal data for the decavanadates of 2,4-, 3,4-, and 3,5- dimethylpyridine and 2,4,6-trimethylpyridine (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 472-473 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Indexed powder patterns of four monoclinic compounds of general formula (BH)3H3V10O28 .xH2O, where x = 1-2.5 and B = 2,4-dimethylpyridine (J8), (C7H10N)3H3V10O28.1.0H2O, 3,4-dimethylpyridine (J10), (C7H10N)3H3V10O28.1.0H2O, 3,5-dimethylpyridine (J11), (C7H10N)3H3V10O28.2.5H2O, and 2,4,6-trimethylpyridine (J12), (C8H12N)3H3V10O28.1.0H2O are given. The cell dimensions of the unit cells with two molecules are: J8 a = 18.360 (2), b = 10.438 (2), c = 13.503 (2) Å, β = 95.99 (1)°; J10 a = 12.538 (3), b = 13.634 (5), c = 16.662 (5) Å, β = 111.82 (2)°; J11 a = 19.483 (5), b = 10.711 (2), c = 13.020 (4) Å, β = 101.52 (2)°; J12 a = 12.776 (3), b = 22.470 (4), c = 11.790 (3) Å, β = 91.54 (1)°.
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    The XIIth Congress of the IUCr, Ottawa, August 1981. An informal report (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 487-489 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Crystallographers (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 490-490 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes and News (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 491-492 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    The f.c.c.+tetragonal two-phase region of the Cu–Ni–Zn system (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 99-102 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: The f.c.c. + tetragonal two-phase region of the Cu–Ni–Zn system has been delineated, and unit-cell parameters along the boundaries determined. Apparently anomalous parameter measurements prevented the determination of the tie lines. A pattern of diffraction broadening from the tetragonal phase common to both the two-phase and single-phase regions was related to the variation in lattice spacing of the tetragonal phase along the boundary. Reasons for this broadening are discussed.
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    Detwinning cell for high-transition-temperature atmosphere-sensitive ferroelastic crystals (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 96-98 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A universal cell is reported for detwinning ferroelastic crystals, with transition temperatures that range from 300 to 1300 K, in a controlled atmosphere. A carefully oriented compressive stress on the order of 0.1–1 MN m−2 is applied to the twinned crystal at room temperature. The crystal temperature is raised from 300 K through the phase transition and is slowly lowered again under stress. The cell has been used to detwin crystals of Na5W3O9F5 with a Curie temperature of 800 K in an atmosphere of flowing high-purity oxygen, and crystals of Rb2KMoO3F3 with a Curie temperature of 328 K in air. Successful detwinning is demonstrable by the complete conversion of high-angle multiple-component line profiles diffracted by the as-grown crystal to single-component reflection profiles.
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    An error assessment of single-crystal 2πdata from four-circle diffractometry (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 126-132 
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    Notes: The criteria developed in the error analysis of 2θ powder data for cubic and uniaxial phases [Frevel (1978). J. Appl. Cryst. 11, 184–189] are extended to biaxial single-crystal data. A methodology is described for applying the focusing matrix method to exhaustive sets of 2θ data for pinacoid and prism reflections measured on a four-circle diffractometer. A spheroidal crystal of hyperpure Si is used to calibrate a Syntex P{\bar 1} automated diffractometer and to establish an effective wavelength for graphite-monochromated Mo Kβ1β3 radiation. A high-quality single-crystal of cis-[bis(7,9-dimethylhypoxanthine) (ethylenediamine)platinum(II)] hexafluorophosphate, [Pt(C2H8N2)(C 7H8N4O)2].(PF6)2, serves as a test case for comparing the normal least-squared analysis with the focusing matrix method. It is concluded that an absolute accuracy greater than one part in 2000 for cell constants of biaxial crystals is difficult to achieve from automated four-circle diffractometer data (2θ ≤ 40°) for non-spheroidal crystals with linear dimensions ca 0.2 mm.
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    Replacement of monochromator and proportional gas counter by mercuric iodide detector in X-ray powder diffraction (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 136-137 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Low-resolution and therefore low-cost mercuric iodide detectors have successfully been applied to replace the combination of a graphite monochromator and a proportional gas radiation counter used in X-ray diffractometers. The mercuric iodide detector requires a lower DC bias of only 200 V rather than the 1500 V bias needed for the proportional gas counter. The much better stopping power of HgI2 allows higher counting efficiency and therefore a better signal-to-noise ratio. Results are shown for X-ray powder diffractions of polycrystalline cubic silicon and tetragonal HgI2.
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    Le tétrabromomercurate(II) de monométhylammonium (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 142-143 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Bis(monomethylammonium) tetrabromomercurate, (CH3NH3)2HgBr4, 2CH6N+.Hg2+.4Br−, is monoclinic, space group P21/c. Unit-cell dimensions are: a = 7.979(4), b = 13.351(4), c = 11.289(4) Å, β = 96.36(2)°, Z = 4, Dm = 3.25, Dx = 3.24 Mgm−3. The compound undergoes a phase transition at low temperature. The JCPDS Diffraction File No. of this compound is 33-1997.
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    Protein model building by the use of a constrained–restrained least-squares procedure (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 144-150 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: The use of a macromolecular model building program, CORELS, which fits a series of constrained groups to a set of approximate guide coordinates, while simultaneously restraining the stereochemistry between groups, is described for protein molecules. The results of an application of this program to hen egg white lysozyme are discussed.
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    Crystal data for antimony molybdenum oxide Sb2MoO6 (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 143-143 
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    Notes: The powder data for antimony molybdenum oxide Sb2MoO6 are reported. This compound is triclinic, P{\bar 1}, with a = 7.481(4), b = 7.504(3), c = 10.120(1) Å, α = 70.43(3), β = 70.91(4), γ = 83.34(7)°; U = 505.9(5) Å3; Z = 4; Dx = 5.74 Mg m−3. The structure is of the fluorite type but it is distorted. Pseudo-monoclinic cells as reported by Parmentier, Courtois & Gleitzer [Bull. Soc. Chim. Ft. (1974), 1–2, 75–77] or that obtained with program TRACER [Lawton & Jacobson (1965). Mobil Oil Corporation Research Department; Lawton (1967). Mobil Oil Corporation Research Department] are also considered and discussed. Neutron diffraction gives further evidence of the triclinic lattice. The JCPDS Diffraction File No. for Sb2MoO6 is 33–1491.
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    Reciprocal lattice and Ewald construction as an experiment for use in lectures (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 157-158 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Microdiffraction from stacking faults and twin boundaries in F.c.c. crystals (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 171-175 
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    Notes: Electron microdiffraction patterns have been obtained from regions of diameter about 15 Å in thin crystals of stainless steel containing twin boundaries and stacking faults. The diffraction spots show splittings which are characteristic of the type of defect present as a result of interference effects in the coherent convergent electron beam. The observations of spot splitting are in good agreement with calculations based on simple theoretical models. In conjunction with previous work on antiphase domain boundaries [Zhu & Cowley (1982). Acta Cryst. A38, 718–724] these results suggest that the observation of spot splitting is of general relevance for the study of all planar faults in thin crystals.
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    Routine recording of diffuse scattering from disordered molecular crystals (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 192-197 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: We describe the use of conventional Weissenberg equipment to record in a routine manner the diffuse scattering from disordered molecular crystals. The diffuse image is digitized using an Optronics P1700 scanner and is corrected for background and other errors before subsequent rewriting as an undistorted reciprocal-lattice section in a form suitable for easy interpretation. The resolution of the method is discussed.
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    A new optical method and apparatus `HAUP' for measuring simultaneously optical activity and birefringence of crystals. I. Principles and construction (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 204-211 
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    Notes: A new and accurate method has been developed by which all the components of the anisotropy of the optical susceptibilities can be determined. The apparatus based on this method has been constructed, and named as HAUP (High-Accuracy Universal Polarimeter). The basic principle is to measure the intensity of the light beam, which is propagated successively through a polarizer, a specimen, and an analyser, as functions of azimuth and deflecting angle from the crossed-Nicols condition. Thus the method is characterized by its extreme simplicity, which prevents systematic errors. Considerations and tests of inevitable systematic errors are made. The systematic errors originating in the parasitic ellipticities of the polarizer and analyser are found to be serious for the measurements of optical activity; appropriate solutions to remove them are devised here. Sensitivities of measurements of optical activity and birefringence by the HAUP method reach 4.8 × 10−8 and 2.2 × 10−6 respectively, the accuracy being 4.2 × 10−3 and 2.2 × 10−3 respectively. By using HAUP it has become possible to measure simultaneously all the components of optical activity, birefringence and rotation of optical indicatrix of any crystals, including those belonging to the monoclinic and triclinic systems. These measurements can be made from about 400 K down to 10 K. Also, simultaneous determinations of electrogyration and electrooptic coefficients have become feasible by applying electric fields to crystals.
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    Double hexagonal superstructure of Au–Mg alloy containing 20 at.% Mg studied by high-voltage high-resolution electron microscopy (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 233-238 
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    Notes: High-resolution observations of Au–20.2 at.% Mg alloy have been carried out by using a 1 MV electron microscope. The many-beam images with the [001] axial illumination are interpreted in terms of the double hexagonal superstructure of 9a0−4H type. With the aid of computer simulations by the multislice method, it is revealed that two kinds of interpretable image are obtained for different specimen thicknesses at the optimum defocus. The imaging conditions are discussed in comparison with the orthorhombic structure of the D023 type.
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    Reciprocal-lattice-compatible representation of linear position-sensitive detector output (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 257-258 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: For the X-ray case relating to a small crystal and not involving a monochromator, the (Δω, Δ2θ) intensity array for a Bragg reflection, derived from use of a linear position-sensitive detector and arranged as for an ω/θ scan, can be relatively simply scaled to correspond with the distribution around a reciprocal-lattice point in the plane of diffraction.
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    Difference thermal analysis of crystalline solids by the use of energy-dispersive X-ray diffraction (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 259-263 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A method is described to study the structural behavior of solids subjected to various temperature programs. The instrumentation consists of a high- or low-temperature device, a temperature programmer, a system for energy-dispersive X-ray diffraction and a data processing and storing unit and allows the fully automatic acquisition of series of spectra. A strong data reduction is performed by summing up difference diagrams. Plotting the resulting values versus temperature yields curves comparable to those obtained by differential scanning calorimetry (DSC) or thermal gravimetry (TG). A kinetic evaluation as used in the case of DSC or TG curves is possible. The method was applied to study the thermal behavior of a mixture of ammonium nitrate with zinc oxide. The curves indicate the strong anisotropic thermal expansion of the ammonium nitrate phase IV below 323 K, its transition to phase II at 325–329 K and the solid-state reaction with zinc oxide within the temperature interval of 353–383 K.
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    A rapid and precise method of measuring Kendrew-model coordinates with theodolites (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 270-273 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: The Kendrew-model coordinates of KDPG aldolase have been measured with the use of two theodolites which are improved versions of a conventional surveyor's transit. The four angular measurements are converted to Cartesian coordinates and a minimum-error estimate with a minicomputer interfaced to the theodolites. The positions of 1677 atoms of the asymmetric unit of KDPG aldolase were measured by two of the authors in four working days or at the rate of about 60 atoms h−1. The standard deviations of the bond distances and angles of the model obtained were ± 0.04 Å and about 7°, respectively. The mathematics of the various conversions are presented.
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    Crystal data for nickel and cadmium α-L-alaninates (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 279-281 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Powder data for bis(α-L-alaninato)nickel(lI) tetrahydrate (monoclinic), bis(α-L-alaninato)cadmium(II) trihydrate (hexagonal) and bis(α-L-alaninato)cadmium(II) (orthorhombic) are reported. Ni(C3H6NO2)2.4H2O: Mr = 306.9, C2, Cm or C2/m, a = 20.34(1), b = 6.48(9), c = 9.73(7) Å, β = 93.0(3)°, V = 1283(28) Å3, Z = 4, Dm = 1.54(3), Dx = 1.56 Mg m−3, Cu Kα (λ = 1.5418 Å); Cd(C3H6NO2)2.3H2O: Mr = 342.6, P3112, P3121, P3212 or P3221, a = 6.37 (1), c = 25.5(7) Å, V = 899(32) Å3, Z = 3, Dm = 1.86(4), Dx = 1.90 Mg m−3, Cu Kα; Cd(C3H6NO2)2: Mr = 288.6, a = 5.45(2), b = 9.19(6), c = 18.08(4) Å, V = 907(11) Å3, Z = 4, Dm = 2.00(5), Dx = 2.11 Mg m−3, Cu Kα. The JCPDS Diffraction File Nos. are: 33-1991 for Ni(C3H6NO2)2.4H2O; 33-1992 for Cd(C3H6NO2)2.3H2O; 33-1993 for Cd(C3H6NO2)2.
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    An interactive program for the interpretation and simulation of Laue patterns (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 281-283 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An interactive Fortran IV program is described which allows the orientation matrix of a crystal to be determined and refined without ambiguity, from a transmission or reflection Laue photograph. The indexing method is that of Riquet & Bonnet [J. Appl. Cryst. (1979), 12, 39–41] applied to a small number of data (less than ten) and adapted for interactive use. The verification of calculated solutions or even the trial-and-error search for the right solution is made by means of the visual comparison between the experimental diagram and simulated patterns displayed on a graphic screen. In addition, the rotation angles for setting the crystal to any new orientation may be computed.
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    Rational functions as profile models in powder diffraction (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 289-294 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Rational functions, the ratio of two polynomials, are shown to be good approximations to powder diffraction profiles. These functions are generalizations of the Lorentzian, the modified Lorentzian, and the profile model of Parrish [Parrish, Huang & Ayers (1976). Trans. Am. Crystallogr. Assoc. 12, 55–73]. The simplest of these functions is of the form f(x) = 1/(1 + A1x2 + A2x4) with constants A1 and A2 that describe the shape of the profile, x = 2θ − 2θ0, and 2θ0 the position of the peak maximum. This function approximates very well Pearson VII distributions with exponents between 1 and 3. An asymmetric profile model with different A1, A2 parameters for the two halves of the peaks was fitted to silicon X-ray powder diffraction profiles and gave unweighted agreement factors from R2 = 0.02 to 0.04 for peaks varying from 28 to 137° 2θ.
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    The determination of crystallite-size and lattice-strain parameters in conjunction with the profile-refinement method for the determination of crystal structures (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 309-316 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: It is shown that the current status of the least-squares profile-refinement method, for the determination of crystal structures from X-ray and neutron powder diagrams, allows the simultaneous determination of crystallite-size and lattice-strain parameters. As profile-shape functions the Voigt, pseudo-Voigt and Pearson VII functions are considered. Formulae are obtained enabling structure refinement and size-strain analysis in the same computer run.
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    Residual stresses in cubic materials with orthorhombic or monoclinic specimen symmetry: influence of texture on ψ splitting and non-linear behaviour (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 325-340 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A quantitative formulation is given of the X-ray diffraction determination of (elastic) lattice deformation in a direction determined by two angles ψ and φ with respect to the specimen frame: the so-called sin2ψ method giving full credit now to crystallographic texture. In most cases of practical X-ray stress analysis, (residual) stresses are evaluated by the traditional sin2ψ, method using quasi-isotropic X-ray elastic constants depending on the lattice plane {hkl} chosen for the measurement but not on the directions φ and ψ. For the case of a textured specimen, however, the single-crystal elastic bitensor components should be coupled to the orientation distribution function (o.d.f.). At variance with most papers published on this subject, which describe the texture using ideal texture components, a general method is developed making full use of relevant o.d.f. theory. It is demonstrated that for orthorhombic specimen symmetry no ψ splitting occurs in contrast with the case of monoclinic specimen symmetry. The theory developed is used to explain some experimental results published previously. All calculations use Reuss's theory of elasticity which neglects the mutual coupling of the crystallites.
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    On `forbidden' reflections in calcia- and yttria-stabilized zirconia (CSZ and YSZ) (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 357-357 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Corrections to a paper by Schoenlein, Hobbs & Heuer [J. Appl. Cryst. (1980), 13, 375–379] are given.
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    A simple method to cut a single crystal in any desired direction (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 360-360 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    Crystallographers (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 360-361 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    Report of the Executive Committee for 1981 (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 361-361 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Small-angle scattering with azimuthal asymmetry (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 384-389 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Small-angle scattering spectra which lack azimuthal symmetry indicate structural anisotropy. For data which exhibit elliptical azimuthal symmetry, the system under investigation has generally been modelled by aligned rotational ellipsoids for the inhomogeneities. It is shown that the scattering centers do not necessarily have to be ellipsoidal, but only that they have azimuthal symmetry around some unique axis within the sample. The scattered intensity may then be described by an ellipsoidal function. The Guinier approximation can also be made for inhomogeneities with only azimuthal symmetry.
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    The growth and perfection of crystals of ammonium dihydrogen orthophosphate, NH4H2PO4. I. Dislocation characterization in self-nucleated crystals (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 390-398 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A combined theoretical analysis and experimental study has been made of the nature of dislocations which propagate in the prismatic and pyramidal growth sectors of ammonium dihydrogen phosphate (ADP). In general the line energies of the dislocations formed in both the sectors are less than 45 eV nm−1. A few higher-energy dislocations (123 eV nm−1) were characterized in the prismatic sectors. The line directions of dislocations which are formed in the pyramidal sectors are such that they propagate towards the growth-sector boundaries and cross into the prismatic sectors. Alternatively, they follow the growth-sector boundaries and emerge at the intersection of adjacent faces. Few, if any, dislocations propagate within these sectors. Consequently, although dislocation-controlled mechanisms of growth may contribute to the growth of the {101} faces of ADP in the early stages of growth, other mechanisms will dominate at longer times. In contrast, the prismatic sectors are more imperfect, containing both screw and mixed dislocations. For these sectors spiral-growth mechanisms are more likely to dominate at all stages of growth.
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    New procedures for quantitative studies of diffuse X-ray scattering (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 407-414 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Equations are derived for errors due to counting statistics in the determination of local order parameters and interatomic displacements from the diffuse X-ray scattering from solid solutions or nonstoichiometric compounds. The Georgopoulous–Cohen procedure is employed, which permits the determination of displacements for individual (AA and BB) pairs. It is shown that certain analysis procedures and a large variation in the ratio of scattering factors through the measured volume in reciprocal space improve the accuracy of the separation of the various contributions to the intensity with this procedure, particularly with respect to the terms due to displacements. Therefore, a short-wavelength radiation (Mo Kα, for example) is sometimes desirable. Weighting the measured intensities with respect to the counting errors also improves the separation. The new procedures also facilitate the analysis of high-temperature measurements and data from ternary systems.
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    Asymmetrically grooved monolithic crystal monochromators for suppression of harmonics in synchrotron X-radiation (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 420-427 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: To suppress unwanted harmonics in crystal-diffracted synchrotron X-radiation, monolithic grooved-crystal monochromators have been studied in theory and experiment. Simply by building non-parallel groove walls in a perfect crystal, the overlap of dynamical diffraction ranges on the two crystals is canceled for higher harmonics, while a partial overlap is preserved for the fundamental, leading to a substantial improvement in fundamental-to-harmonics ratio in the diffracted beam. A grooved silicon 111 monochromator with wall angles of 0 and 7° delivers a beam of harmonic contamination better than 3.3% at fundamental wavelengths between 1.2 and 1.6 Å with a beam intensity exceeding 50% of that available from a standard channel-cut crystal. Silicon 331 and 511 versions can achieve harmonic contaminations well below 0.1%. Asymmetrically grooved monochromators can work as stable wavelength scanners free from harmonics requiring no delicate control of angle.
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    Crystal data for rhombohedral Pb3[Ge2O7]isotypic with Pb-barysilite (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 430-430 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Metastable barysilite-like Pb3[Ge2O7] was obtained from the melt at a sufficiently high cooling rate together with stable Pb5Ge3O11, α-PbGeO3, and a homologous series of other metastable lead germanates. The crystal data derived from an indexed powder diagram are a = 10.2960(6), c = 39.805(4) Å, space group R{\bar 3}c, Dm = 7.18, and Dx = 7.188 Mg m−3 for Z = 18. The JCPDS Diffraction File No. for Pb3[Ge2O7] is 33-1487.
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    Notes and News (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 438-438 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    A variable-temperature sample container for low-temperature neutron powder diffraction (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 449-452 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A variable-temperature sample container was developed for the neutron powder diffraction study of crystal structures and phase transitions in solidified gases. It consists of two coaxial tubes made of boron-free fused silica and fitted with heating coils and thermocouples. The exchange space between the tubes is filled with low-pressure helium gas controlled by two fine needle valves. Used in conjunction with a centre-stick-type liquid-helium cryostat and a proportional temperature controller, it maintains a powder sample of about 8 cm3 volume at a constant temperature anywhere in the 4.2 to 77.4 K temperature range. Its stability is not worse than ±0.15 K and the liquid-helium consumption is about 1 litre a day above 17 K, increasing up to 6 litres a day at lower temperatures. It can also be used for the preparation of fine-grained powder samples directly from the gas phase.
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    An absolute intensity standard for small-angle X-ray scattering measured with position-sensitive detectors (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 473-478 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Silica sols have been evaluated as a means of determining the incident beam intensity using position-sensitive detectors. Analysis of the total integrated small-angle X-ray scattering yielded an electron density of the suspended silica particles that was within 4% of the electron density of amorphous silica. The sols were found to be particularly well suited for use with position-sensitive detectors and represent a convenient, rapid, and accurate means to determine the incident beam intensity.
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    Assessment of parameter accuracies in profile analysis of white-beam neutron powder diffraction experiments (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 479-485 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: One of the problems arising in profile analyses of white-beam powder diffraction experiments is that in order to assess the reliability of the refined structure parameters allowance must be made not only for errors in the actual powder data but also for uncertainties in the various wavelength-dependent corrections involved. As a means for such assessments the present work provides a general method in which the incident white neutron flux spectrum is assumed to be measured and combined with the other wavelength-dependent factors to form a set of effective incident intensities with known statistical properties for the diffraction peaks. Given that appropriate models are used for both the powder spectrum and the effective fluxes, the unknown model parameters and their accuracies can be estimated optimally through a single least-squares fit of the available experimental data. By applying the formalism to a real nickel powder measurement, it was shown that the precision of the parameter estimates may depend considerably on the errors of the wavelength-dependent corrections, unless these are known with much higher accuracies than the diffraction pattern. In the example this proved true especially for the scale factor and the temperature factor.
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    Diffraction line profiles and Scherrer constants for materials with hexagonal crystallites (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 512-518 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Diffraction line profiles and Scherrer constants for use with various measures of diffraction broadening are derived for right hexagonal prisms. A method is described for obtaining the size of crystallites with this form and a comparison is made with a cylindrical model. The technique is applied to annealed ZnO powder obtained from the thermal decomposition of Zn3(OH)4(NO3)2. The Fourier method is used to show that the crystallites are hexagonal prisms with an average height and edge length of 213 and 87 Å and with the z axis parallel to the axis of the prism and x or y parallel to an edge.
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    Monolithic double-grooved-crystal monochromators with tunable harmonic suppression for neutrons and X-rays (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 524-531 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The principal methods of employing double-crystal reflection for harmonic rejection are briefly reviewed. The effect of using non-equal d spacings (dispersion) is considered. A new type of perfect-crystal monochromator consisting of a monolithic combination of a pair of grooved crystals a and b is described. The monochromaticity (degree of harmonic suppression) M(β) is tuned by tilting groove a with respect to groove b by an appropriate angle β. The tilting is achieved in a simple way through a pair of helical springs. With three reflections in the first and two reflections in the second groove M(β0) values between about 300 and 100 have been measured for X-rays at energies ranging from 6.72 to 9.86 keV and at a bandwidth ΔE/E∼1.5%. β0 is the tilting angle for which M(β) is optimized. Once aligned the monochromator is a very simple unit, which can be mounted on any standard goniometer head and which can be used for both X-rays and thermal neutrons.
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    Eccentricity corrections for a modified Debye–Scherrer camera (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 532-534 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: By substituting a thin flat powder specimen for the conventional cylindrical sample in a modified Debye–Scherrer camera [Frevel, DeLeeuw & Albe (1982). Norelco Rep. 29, 2, 38–39], well defined diffraction profiles representative of the entire sample are obtained. The peak of such a diffraction profile can be measured quite accurately so that for that reflection the effective center of the diffracting sample may be determined from the bracketing diffraction peaks of an internal standard.
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    Detector aperture size in the conventional estimation of integrated intensity in the \def\lambdabar{\ifvmode\noindent\fi{\hbox{$\lambda$}\kern-0.35em\raise0.7ex\hbox{-}\kern0.2em}}\lambdabar"/20 scan mode (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 572-573 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: In respect of the traditional wide-aperture procedure for the measurement of integrated intensity, the practice of varying the detector aperture width from reflection to reflection as a function of tan θ is shown to be erroneous in relation to the ω/2θ scan mode: in most cases, no adjustment is needed at all.
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    Crystal data for Rb2CoCl4.2H2O (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 575-575 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: This compound is triclinic, probably isostructural with Rb2MnCl4.2H2O, the space group is P1 or P{\bar 1}, a = 6.50 ± 0.04, b = 6.99 ± 0.04, c = 5.58 ± 0.03 Å, α = 92.8 ± 0.1°, β = 97.2 ± 0.1°, γ = 65.4 ± 0.1°, V = 228.76 ± 0.06 Å3, Z = 1, Dm = 2.94 ± 0.03, Dx = 2.96 g cm−3. The precession method and Zr-filtered Mo Kα radiation (γ = 0.7107 Å) were used. The description of the specimen preparation, chemical analysis, morphology and comparison with similar substances have been deposited.
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    Crystal data for CuGaxIn1−xTe2 (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 576-576 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A series of samples in the system CuGaxIn1−xTe2, 0 ≤ x ≤ 1, has been synthesized and characterized by X-ray diffraction. All the samples have a chalcopyrite-type structure, the unit-cell parameters a and c and the ratio c/a changing linearly with x. The unit-cell parameters for the compounds with x = 1, 0.80, 0.65, 0.50, 0.30, 0.15 and 0 and the powder diffractometer data for x = 1, 0.5 and 0 are given at 298 K. CuGaTe2: a = 6.021(2), c = 11.937(5) Å, V = 432.75 Å3, Dx = 5.96 g cm− 3; CuGa0.80In0.20Te2: a = 6.053(2), c = 12.039(4) Å, V = 441.09 Å3, Dx = 5.99 g cm− 3; CuGa0.65In0.35Te2: a = 6.084(2), c = 12.107(7) Å, V = 448.14 Å3, Dx = 5.99 g cm−3; CuGa0.50In0.50Te2: a = 6.107(2), c = 12.177(7) Å, V = 454.15 Å3, Dx = 6.01 g cm−3; CuGa0.30In0.70Te2: a = 6.144(2), c = 12.296(7) Å, V = 464.16 Å3, Dx = 6.01 g cm−3; CuGa0.15In0.85Te2: a = 6.168(3), c = 12.355(10) Å, V = 470.04 Å3, Dx = 6.03 g cm−3; CuInTe2: a = 6.195(2), c = 12.418(6) Å, V = 476.58 Å3, Dx = 6.04 g cm−3. The JCPDS Diffraction File Nos. are: 34-1500 for CuGaTe2; 34-1498 for CuInTe2; 34-1499 for CuGa0.50In0.50Te2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988301105X
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