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  • International Union of Crystallography (IUCr)  (2,373)
  • 1980-1984  (1,004)
  • 1975-1979  (1,369)
  • 1925-1929
  • 1981  (1,004)
  • 1979  (1,369)
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  • 1980-1984  (1,004)
  • 1975-1979  (1,369)
  • 1925-1929
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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 12 (1979), S. 628-628 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An interactive program using a graphic display device for the analysis of small-angle scattering has been developed. It includes the curve fitting of experimental data to theoretical results calculated through a triaxial body approximation.
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  • 2
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 3-7 
    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.
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  • 3
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 24-27 
    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.
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  • 4
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 43-50 
    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.
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  • 5
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 60-61 
    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.
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  • 6
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 61-62 
    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.
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  • 7
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 64-65 
    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.
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  • 8
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 68-68 
    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.
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  • 9
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 85-93 
    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.
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  • 10
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 124-130 
    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.
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  • 11
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 117-123 
    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.
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  • 12
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 137-139 
    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.
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  • 13
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 139-141 
    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.
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  • 14
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 145-148 
    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.
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  • 15
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 151-153 
    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.
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  • 16
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 160-168 
    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.
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  • 17
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 370-382 
    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.
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  • 18
    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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  • 19
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 432-436 
    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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  • 20
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 444-446 
    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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  • 21
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 455-461 
    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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  • 22
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 465-465 
    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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  • 23
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 12 (1979), S. 1-9 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Two-dimensional X-ray diffraction patterns may be recorded quantitatively by means of X-ray-to-electron converters which are scanned in a television-type raster scan. Detectors of this type are capable of operating over the whole range of counting rates from very low to higher than those with which other types of converters can deal. The component parts of an X-ray television detector are examined and the limits to the precision of the measurements are analysed.
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  • 24
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 12 (1979), S. 19-24 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: X-ray holography schemes are analyzed. It is shown that they have a very low aperture ratio, and this limits the size of objects from which a hologram can be recorded. It is indicated that holography schemes can be constructed on the basis of the methods of X-ray diffraction optics.
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  • 25
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 491-491 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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  • 26
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    Applied crystallography online 12 (1979), S. 42-48 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The Fourier transform values are obtained by multiplying the integrated intensities by the correction factor C(h). The problem of calculating the correction factor for biological specimens which have a multilayered structure is treated. Allowance is made for the transverse size of the specimen, the disorientation in the specimen (ω), the divergence of the X-ray beam (ε), the size of the repeating unit and the curvature of the sphere of reflection. The correction factor C(h) is given by C(h) = Ω[1 + 2γh2]1/2 exp (πδ2)exp (−Ω2[1 + 2γh2]), where γ = (ω2 + ε2)/2(Ω2d2) and where Ω is the diameter of the hth order disc when ω = ε = 0. The formula for C(h) applies to specimens which remain stationary during the X-ray experiment.
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  • 27
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    Applied crystallography online 12 (1979), S. 54-56 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The transition temperature of ferro- and antiferroelectric crystals can be simply determined by continuous pyroelectric temperature analysis (PTA) of unsintered pressed powder. In order to avoid excessive stored charge the samples were not previously treated by a polarizing electric field. Experiments performed with (NH4)2SO4, KH2PO4 and NH4H2PO4 showed the transition points with a precision of 1°C.
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  • 28
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    Applied crystallography online 12 (1979), S. 57-59 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Five new PbI2 polytypes, 8H(1232), 10H(11112112), 10H(112222), 22H[11(22)5] and 30R[111313]3, were solved by the X-ray diffraction method. It was found on polytypic change that (a) the 2H polytype is changed into various polytypes on heating at 130°C and most of these further change to 12R[13]3 on heating at 260°C; (b) the polytypes 4H, faulted 4H, 14H, 22H, 26H and 30R with layer structures similar to the 12R[13]3 are fairly stable at high temperatures; (c) the 2H-30R [111313]3 transformation occurs reversibly.
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  • 29
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    Applied crystallography online 12 (1979), S. 66-69 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The reactivity of hematite depends among other factors on the morphology of the crystal. The choice of the orientation of the reference axes has been made with the help of stereographic projection combined with the morphology of the etch figures on the different faces of the crystal. That the most stable face of a crystal corresponds to the composition plane is shown for crystals of hematite from Elba.
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  • 30
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    Applied crystallography online 12 (1979), S. 70-77 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The lattice defects of beryl single crystals from Brazil and Madagascar have been studied by X-ray topography. Two types of linear defects are observed: channels and grown-in dislocations. Slip systems and Burgers-vector moduli are determined. Some calculations of directions of minimum dislocation energy are given and they are in quite good agreement with the observations.
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  • 31
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 12 (1979), S. 60-65 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: At present, over 30 000 powder diffraction patterns are available as references. It is proposed that the patterns on file as well as new patterns submitted for publication be assigned quantitative quality factors. A simple-to-use figure of merit, FN, covering both accuracy in the measurement of the positions of the diffraction lines and completeness of the pattern, has been derived: FN = (1/|{\bar \Delta 2 \theta}|) (N/Nposs), where Nposs is the number of independent diffraction lines possible up to the Nth observed line and |{\bar \Delta 2 \theta}| is the average absolute discrepancy between observed and calculated 2θ values. This figure of merit provides a rapid evaluation of powder patterns, in much the same way as the R factor provides a rating for single-crystal structure determinations. This figure of merit also provides a means to assess the reliability of a unit derived solely from powder data. At present FN ranking scheme is shown to be superior to de Wolff's M20 for ranking patterns. It is recommended that use of the latter be discontinued for that purpose. Guidelines are given on the use and implementation of the FN rating of powder diffraction patterns.
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  • 32
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    Applied crystallography online 12 (1979), S. 126-126 
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    Notes: A standard Debye–Scherrer camera can be readily converted to operate in the Gandolfi mode by the addition of a simple attachment. The attachment replaces the usual camera cover; no changes to the original powder camera are required and its inherent accuracy is preserved.
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    Applied crystallography online 14 (1981), S. 226-229 
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    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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    Applied crystallography online 12 (1979), S. 129-130 
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    Notes: The title compound was recognized from the new and unexpected powder pattern of aged precipitates obtained by mixing solutions of excess silver nitrate and sodium thiosulphate under specified conditions. The possible crystalline impurities were identified and conditions were established to yield a pure product. The brown microcrystalline material is tetragonal with a = b = 7.201; c = 10.220 Å. It is a solid electrolyte, has an irreversible transition point at 246°C and melts at 405°C. Method of preparation and powder data are given.
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    Applied crystallography online 12 (1979), S. 133-134 
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    Notes: Two Fortran programs have been written. The first determines the coordinates of points on a standard stereographic projection, and the second plots these points. The programs may also be used to draw pole figures of so-called `ideal' sheet textures.
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    Applied crystallography online 12 (1979), S. 131-132 
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    Notes: Powder data for a previously unreported dehydration product of fluorapophyllite (KCa4Si8O20F.8H2O) are presented. The reflexions are indexed on the basis of a tetragonal cell with a = 6.937 ± 0.003 and c = 8.488 ± 0.004 Å, (c/a = 1.2235 ± 0.0008). The d spacings and intensities correspond to the unindexed data for CaF2.SiO2 in the JCPDS file (Card No. 20-1050) and the refined cell dimensions are identical, to within the experimental error. Single-crystal data have not yet been obtained for this phase.
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    Applied crystallography online 12 (1979), S. 134-134 
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    Notes: A computer program has been written for the evaluation of integrated intensities from X-ray diffractometer data. It has been compiled for IBM 360/65 and HP 2100A. The Lehmann–Larsen profile-analysis method [Lehmann & Larsen (1974). Acta Cryst. A30, 580–584] has been used. For weak reflections, profiles obtained from well defined, neighbouring reflections are employed.
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    Applied crystallography online 12 (1979), S. 135-135 
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    Applied crystallography online 12 (1979), S. 136-136 
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    Applied crystallography online 12 (1979), S. 135-136 
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    Applied crystallography online 12 (1979), S. 137-137 
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    Applied crystallography online 12 (1979), S. 137-138 
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    Applied crystallography online 12 (1979), S. 138-138 
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    Applied crystallography online 12 (1979), S. 138-138 
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    Applied crystallography online 12 (1979), S. 138-138 
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    Applied crystallography online 12 (1979), S. 138-139 
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    Notes: In all organisms the multi-subunit enzyme DNA-dependent RNA polymerase catalyses the first basic step in gene expression, the transcription of DNA into RNA. The neutron small-angle scattering effects were studied in the Guinier region by applying the contrast-matching technique. Isotopic labelling was realised by culturing fully deuterated E. coli cells in a heavy-water medium containing deuterated substrates. One or two completely deuterated components (subunits) of polymerase holoenzyme (composition formula α2ββ′σ, molecular weight 497000) were recombined with the remaining natural (`hydrogenated') subunits for these neutron measurements. Measurements are presented of radii of gyration R, overall shapes, and pair distances d, of three components (subunits α2β,β′) in RNA polymerase of E. coli. The subunits β′, β and α2 are obviously rather elongated in situ and exhibit (as scattering-equivalent prolate ellipsoids) axial ratios of about 7:1 up to 9:1. The intersubunit centre of gravity distances were analysed to be 7.3 ± 0.8 nm for β−β′, 8.2 ± 1.2 nm for α2−β′ and 7.0 ± 1.7 nm for α2−β.
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    Applied crystallography online 12 (1979), S. 186-191 
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    Notes: It is demonstrated experimentally that the well known spin-selective deflection of neutrons transmitted through a static magnetic field region with triangular geometric boundaries combined with the high angular resolution of a non-dispersive double-crystal arrangement can be used to polarize a thermal neutron beam to a degree close to unity at reasonably low laboratory fields of 1.0 to 1.5 T.
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    Applied crystallography online 12 (1979), S. 192-200 
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    Notes: A long-wavelength neutron scattering facility at the SAFARI-1 reactor is described. Neutrons of wavelength between 5 and 15 Å can be selected. Features of the facility are the use of microwave guides as neutron conductors, flexible guide-pipe configuration and automatic sequential sample changing. Examples are given of measurements on radiation-induced voids in copper, aluminium, Al-0.4%Si and Al-0.1%In after neutron irradiation and magnetic scattering in US and in 80US-10UC-10UC2.
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    Applied crystallography online 12 (1979), S. 201-204 
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    Notes: The development is critical in recording X-ray topographs since it takes a long time and determines the final quality of the pictures. It is shown that, in most cases, it is possible to decrease both exposure time and development time and still obtain pictures of good quality. Standard conditions of development should be used to achieve higher resolution only. This new standard may be of great use with the modern high-power sources.
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    Applied crystallography online 12 (1979), S. 205-208 
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    Notes: The doping method in quantitative X-ray diffraction phase analysis is described. The method involves the addition to the investigated system of known amounts of the components, the weight fractions of which are to be simultaneously determined. The weight fraction of a component is related to the intensities diffracted by that component and by any non-added component, before and after doping. The method can also be applied to systems containing unidentified components by analysing for only those components of interest, as well as for amorphous-content determination.
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    Applied crystallography online 12 (1979), S. 209-220 
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    Notes: A method for quantitative determination of local curvature in elastically bent perfect crystals is described. The method is based on X-ray intensity measurements, and a comparison of experimentally determined values with those derived from diffraction theory gives satisfactory agreement. The method was applied to determine the strain gradient and strain concentration in the vicinity of the notch of an elastically bent crystal. The experimental results were compared with those derived from a similar model based on continuum mechanics. Possible applications of the X-ray method are discussed to obtain experimental solutions to strain analyses which, when approached by continuum mechanics, pose formidable mathematical obstacles.
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    Applied crystallography online 12 (1979), S. 239-239 
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    Notes: 1,5-Dichloroanthraquinone undergoes a solid-state transformation at 470 K. The two modifications are very similar, except that a is greater than b above the transition temperature and the inverse is true at room temperature.
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    Applied crystallography online 12 (1979), S. 221-224 
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    Notes: A film-type X-ray high-temperature (up to about 2250 K) powder camera using the Guinier focusing principle in transmission is described. Use is made of a germanium monochromator. The powder specimen is spread without adhesive on a horizontal supporting film of refractory material, and rotates about a vertical axis. The support is surrounded by a cylindrical furnace of thin tantalum sheet enclosed in a chamber which can be evacuated or filled with an inert gas. The X-radiation enters and leaves the chamber through beryllium windows. The film holder is situated outside the chamber. The sample temperature is measured by thermocouples and optical pyrometry. Problems due to the coating by evaporated material of the silica glass window used to observe the specimen are obviated by the use of a transparent shield which can be rotated to give fresh surfaces when needed.
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    Applied crystallography online 12 (1979), S. 241-242 
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    Notes: Cs2[Pd(CN)4].H2O and Cs2[Ni(CN)4].H2O were found to be isotypic with the known hexagonal Pt compound which shows an unusual helical chain of six [Pt(CN)4]2− groups in the unit cell, space group P61 or P65. The crystal data are a = 9.559 (2) and c = 19.308 (4) Å, Dm = 2.87 (4), Dx = 2.912 Mg m−3 for the Ni compound, and a = 9.704 (2), c = 19.388 (4) Å, Dm = 3.12 (4), Dx = 3.115 Mg m−3 for the Pd compound. X-ray powder data are given.
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    Applied crystallography online 12 (1979), S. 244-244 
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    Notes: Na3Mg2P5O16 is monoclinic, P21/c, Z = 2, with unit-cell parameters a = 5.177 (1), b = 6.853 (1), c = 18.628 (5) Å, β = 90.00 (4)°.
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    Applied crystallography online 12 (1979), S. 262-262 
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    Applied crystallography online 12 (1979), S. 267-274 
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    Notes: The filter theory allows one to compare the efficiencies of smoothing procedures widely used in the field of small-angle X-ray scattering. This method is demonstrated for polynomial fitting and modified frequency filtering. Optimized and objective smoothing parameters are determined for both procedures through the knowledge of variance reduction factors, transfer functions of the filters, the largest value of the spatial frequencies of the scattering curve and the distortions caused by the smoothing procedures. The comparison of the efficiency of polynomial fitting and frequency filtering clearly shows the superiority of the latter; therefore, this method has to be preferred.
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    Applied crystallography online 12 (1979), S. 332-338 
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    Notes: The influence of orientation on the powder diagrams produced by lamellar structure systems is studied in the case where the bidimensional lattice is very limited and where the layer structure is complex. The orientation distribution must be included in the numerical integration which leads to the line diffraction profile. The technical measurement of the real experimental orientation is discussed. An example is given showing the influence of the orientation on the interference function in the absolute scale.
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    Applied crystallography online 12 (1979), S. 339-345 
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    Notes: Defocusing errors associated with the use of a one-dimensional position-sensitive proportional counter on a powder diffractometer are considered. These errors are small in the measurement of residual stress and it is not necessary to apply mathematical corrections, especially if the X-ray tube is aligned properly. Correspondingly, these errors are small for high-angle peaks in any reflection experiment compared with the present detector resolution. The equations presented allow for an evaluation of this error in most equipment configurations.
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    Applied crystallography online 12 (1979), S. 351-356 
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    Notes: A method is described whereby the complete distribution of first-nearest-neighbor atomic configurations can be determined from experimental short-range order coefficients for binary substitutional f.c.c. alloys. The process involves the computer simulation of the structure represented by the experimental αi by a Gehlen–Cohen-type procedure, followed by the classification of each atom of a given species in the model as one of the 144 crystallographically distinct nearest-neighbor types. These simulation and searching procedures are then used to demonstrate the consistency of the information one can expect to obtain from a given set of αi by `close fitting' to different numbers of coordination shells. It is shown, for example, that a six-shell close fit to a selected set of αi can yield a solution with a mean relative deviation of about five per cent for the nearest-neighbor configuration concentrations.
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    Applied crystallography online 12 (1979), S. 357-359 
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    Notes: Simple methods of aligning four-circle diffractometers with crystal reflections are devised. They provide the methods to check (1) perpendicularity of χ plane to the incident beam, (2) zero point of 2θ and linearity of focus-χ center-receiving aperture and (3) zero point of χ.
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    Applied crystallography online 12 (1979), S. 399-400 
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    Notes: Experimental values of the cross sections of Al, Si, Cu, Zn, Ge, Pb and Bi at room temperature for several neutron energies between 2 × 10−3 and 10−1 eV, are reported. The measurements were repeated for a Bi single crystal at T = 80 K.
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    Applied crystallography online 12 (1979), S. 401-402 
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    Notes: Some materials of low absorption that contain particles in the several thousand Å range can produce an intensity of small-angle scattering that is a significant fraction of that of the transmitted beam. This is quite apparent in the range of a few s scattering angle when a Bonse–Hart small-angle scattering diffractometer is used. A method was developed that allows an accurate absorption correction to be calculated when the scattering by the sample can be approximated by an exponential function in the range of 0 to 5 s double Bragg angle 2θ. Variation of sample thickness allows the correction method to be checked.
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    Applied crystallography online 12 (1979), S. 405-406 
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    Notes: An indexed powder pattern is reported for Mg2Na4O10Si3. The unit cell is orthorhombic, a = 10.584 (7), b = 14.328 (7), c = 10.457 (7) Å. Transition to a cubic phase, a = 7.440 Å, occurs at 918 K. A Na-deficient tetragonal phase was also observed.
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    Applied crystallography online 12 (1979), S. 403-404 
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    Notes: A simple yet effective high temperature furnace for heating crystals or powder specimens for neutron diffraction studies on a θ/2θ diffractometer is described. The furnace can maintain samples at temperatures up to 1573 K, in air, with a stability of ± 4 K for periods of many hours. Specimen temperature is uniform within 12 K, or much less with the use of a silica sleeve.
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    Applied crystallography online 12 (1979), S. 407-410 
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    Notes: Indexed powder diffraction data are presented for Ca3Al2O6 and its sodium-containing solid solutions. Powder patterns of the cubic and orthorhombic phases calculated from the crystal structure data are compared with the observed patterns. Indexed data are presented for the monoclinic phase, which is stabilized by sodium and silicon. The so-called tetragonal phase is shown by electron diffraction to be orthorhombic, pseudo-tetragonal. It probably has the symmetry Pcaa with a = b = 10.8599 (9), c = 15.1234 (20) Å.
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    Applied crystallography online 12 (1979), S. 413-413 
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    Notes: Crystal data for promethazine picrate (C23H23N5O7S) complex are: triclinic P1 or P{\bar 1}, Z = 2, a = 18.49 (1), b = 7.77 (1), c = 7.79 (1) Å, α = 70.9 (2), β = 90.0 (2), γ=83.0 (2)°.
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    Applied crystallography online 12 (1979), S. 414-415 
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    Notes: Tris(2-cyanoethyl)phosphine oxide, OP(C2H4CN)3, C9H12N3OP, is hexagonal (rhombohedral), space group R3c, with a = 13.484 (1) and c = 10.162 (1) Å. The sulphide and selenide are triclinic, space group P{\bar 1}. Cell dimensions for SP(C2H4CN)3, C9H12N3PS, are a = 8.363 (8), b = 9.026 (4), c = 9.777 (6) Å; α = 98.75 (4), β = 107.31 (5), γ = 115.85 (5), and for SeP(C2H4CN)3, C9H12N3PSe, a = 8.497 (5), b = 9.148 (2), c = 9.972 (8) Å; α = 98.85 (2), β = 107.20 (6), γ = 116.96 (3)°. X-ray powder diffraction data are quoted.
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    Applied crystallography online 12 (1979), S. 488-488 
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    Applied crystallography online 12 (1979), S. 488-488 
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    Applied crystallography online 12 (1979), S. 502-510 
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    Notes: The study by neutron small-angle scattering of reverse-type micellar solutions of the ternary system water–OT aerosol–n-heptane is reported. The contrast variation method used both on the water inside the micelle and on the solvent makes it possible to determine some structural parameters of the micelle and to propose two micellar models.
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    Applied crystallography online 12 (1979), S. 489-501 
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    Notes: In recent years, nonlinear d versus sin2 ψ distributions have been observed in stressed materials which cannot be explained by the classical fundamentals of X-ray stress measurement, d is the interplanar spacing measured and ψ is the angle between the surface normal of the sample and the measuring direction. This paper reviews treatments for these nonlinear distributions, including stress gradients, shear stresses and anisotropic X-ray elastic constants. Methods for the evaluation of stresses are reported, and recommendations are given for the practical application of X-ray stress measurement.
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  • 74
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    Applied crystallography online 12 (1979), S. 511-516 
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    Notes: High-pressure time-of-flight neutron diffraction studies have been carried out on orthorhombic Ge2N2O to 25.4 × 108 Pa and by X-ray diffraction to 49 × 108 Pa. The zero-pressure axial compressibility coefficients are Ka = 33 (2), Kb = 41 (2), Kc = 28 (2), and volume Kv = 99 (5) × 10 −13 Pa−1. The changes in bond angles and bond lengths at pressures from 105 to 25.4 × 108 Pa have been measured. The structure of Ge2N2O consists of GeN3O tetrahedra linked along the a direction by Ge–O–Ge bonds and along the b and c directions by three coordinated Ge–N bonds. This structural framework adjusts to applied pressure by tetrahedra tilting in a cooperative fashion, the biggest change being observed in the Ge–O–Ge angle which decreases by 12.4°. The behavior of Ge2N2O is very similar to its isomorph Si2N2O, though the tetrahedra deform somewhat more for Ge2N2O. The pressure changes in the lattice parameters of Ge2N2O up to 8̃ × 108 Pa are very similar to those of Si2N2O up to 2̃4 × 108 Pa, supporting the contention that germanates behave as high-pressure models for silicates.
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  • 75
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    Applied crystallography online 12 (1979), S. 517-524 
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    Topics: Geosciences , Physics
    Notes: A Monte Carlo model is developed to simulate the X-ray fluorescence process within a homogeneous multi-element mixture. Validation of the model is obtained through comparison of the model's predictions with experimental data for the iron–nickel–chromium system, for which the inter-element effects are severe. The results indicate that the Monte Carlo model is an excellent simulator and may be used in place of a set of standards to determine the influence coefficients for analysis of fluorescence data.
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  • 76
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    Applied crystallography online 12 (1979), S. 531-536 
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    Topics: Geosciences , Physics
    Notes: Test experiments were made using the X-ray energy-dispersive method at the storage ring DORIS (Hamburg) working in the single-bunch mode. It is shown that the spectral distribution of the incident beam calculated from the storage-ring parameters is in very good agreement with that derived from measured diffraction patterns of known substances, and thus it can be used for structural studies. This is illustrated with results of profile-fitting refinement applied to urea (CH4N2O) and naphthalene (C10H8). It is also shown that because of an improved detector system and the time structure of the radiation emitted from the storage ring one is able to record 7 × 104 photons per second and obtain reliable patterns in times of the order of 1 s.
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  • 77
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    Applied crystallography online 12 (1979), S. 525-530 
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    Topics: Geosciences , Physics
    Notes: Synchrotron-radiation Laue patterns give valuable information on the sizes and shapes of grains in a polycrystalline material even if these are too small for synchrotron topography. A calculation, based on kinematic theory, is presented for the radial and lateral broadening of the diffraction spots obtained with white radiation. The most conspicuous broadening is to be expected when the dimensions of the reflecting planes are small and not their number; this is at variance with the conditions leading to broadening with conventional monochromatic methods. Quantitative assessment of the crystal dimensions is possible if auxiliary spectral information is obtained by using selectively absorbing filters. The theory was applied to the analysis of Laue photographs of xenon and krypton crystallites condensed on a cooled beryllium substrate. Crystal dimension down to a few nanometers could be determined. The method is, in principle, applicable to the determination of the grain size and shape distribution of fine-grained polycrystalline samples of any material. Changes during crystallization and recrystallization can be easily followed by virtue of the simple experimental set-up and short exposure times involved.
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  • 78
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    Applied crystallography online 12 (1979), S. 537-544 
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    Notes: A Be-walled conduction cooling He(l) cryostat intended for the interval 20–80 K and the κ geometry of the CAD4 X-ray diffractometer is described. Three-dimensional X-ray intensity data can be collected in the interval − 45 〈 χ 〈 45° with the temperature stability maintained within ± 1 K. The experimental problems caused by centering an unseen crystal and by the absorption and scattering in the Be walls are discussed. D(+)-tartaric acid, C4H6O6, was chosen as a test compound. Only minor differences occur in its crystal and molecular geometry between 295 and 35 K.
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  • 79
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    Applied crystallography online 12 (1979), S. 545-550 
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    Notes: Intensity profiles of diffuse streaks along [111] were accurately measured for heavily faulted regions in deformed specimens. They often showed two or three broad peaks and differ remarkably from Paterson's [J. Appl. Phys. (1952). 23, 805–811] profiles (Reichweite s = 1), but are in fairly good agreement with Kakinoki's [Acta Cryst. (1967). 23, 875–885] profile of s = 2 with the sequence probabilities α1 = 0.45–0.85 and α2 = 0–0.1. This means that the deformation (intrinsic) faults are produced more easily on every other (111) plane than on successive planes. A model which shows the distribution of the deformation faults is constructed by a computer simulation. A detailed study using Kakinoki's theory with s = 3 shows a better fit with the experimental profile.
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  • 80
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    Applied crystallography online 12 (1979), S. 551-553 
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    Topics: Geosciences , Physics
    Notes: The intensities of two-dimensional reflections from a non-graphitic carbon were correctly calculated by using the general Debye scattering equation and the hypothesis of small (about 12 Å in diameter) domains diffracting incoherently with respect to one another.
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  • 81
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    Applied crystallography online 12 (1979), S. 564-569 
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    Notes: A texture goniometer has been built specifically for geologic applications. Features include (1) a large and variable radius, (2) a variable collimation system that is simple to use and which permits excellent resolution, (3) a wide main circle that allows large specimens to be analysed, (4) partial vacuum paths for the incident and diffracted beams, (5) a θ:2θ drive that allows 2θ scans. The performance of the goniometer is assessed by determining resolution and count rate for various collimations and radii.
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  • 82
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    Applied crystallography online 12 (1979), S. 554-563 
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    Topics: Geosciences , Physics
    Notes: An analysis of the Rietveld profile refinement method used in the interpretation of neutron or X-ray powder diffraction patterns has been carried out. It is shown that the values obtained for the structural parameters are not exactly the same as those obtained from an integrated intensity refinement of the same data and that the standard deviations of the parameters are determined incorrectly. Whilst the differences in the values of the parameters may not be statistically significant, the fact that their standard deviations are estimated incorrectly severely limits their usefulness. These conclusions are confirmed by refinement of a number of data sets using both methods and in most of these cases the standard deviations are found to be underestimated by the profile refinement method by a factor of at least two. Discussions based on the results of profile refinement must therefore be reconsidered and the relative value of powder diffraction techniques must be reviewed.
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  • 83
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    Applied crystallography online 12 (1979), S. 609-610 
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    Topics: Geosciences , Physics
    Notes: Acid monophosphates MII(H2PO4).2H2O with MII = Mn, Fe and Co are isotypic with the corresponding Cd and Zn salts. Crystal data and powder diffraction data for these three salts are given.
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  • 84
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    Applied crystallography online 12 (1979), S. 611-611 
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    Notes: Ammonium magnesium carbonate tetrahydrate crystallizes with an orthorhombic unit cell, a = 7.697, b = 10.287, c = 6.639 Å, Z = 2; Dx = 1.595, DM = 1.61 ± 0.01 Mg m−3. An indexed powder pattern is given.
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  • 85
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    Applied crystallography online 12 (1979), S. 612-612 
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    Notes: The powder data for pipemidic acid trihydrate are reported. This compound is triclinic with a = 8.570 (3), b = 8.514 (3), c = 15.208 (6) Å, α = 105.14 (4), β = 110.84 (5), γ = 113.96 (5)°. Z = 2.
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  • 86
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    Applied crystallography online 12 (1979), S. 613-614 
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    Notes: Indexed powder patterns of three monoclinic phases of sodium propanoate, Na+.C3H5O2−, are given. The cell dimensions are a = 3.624 (3), b = 5.338 (4), c = 11.414 (8) Å, β = 90.84 (3)° at 507.7 K; a = 3.622 (3), b = 5.359 (5), c = 11.400 (10) Å, β = 90.58 (2)° at 489.8 K and a = 3.569 (3), b = 5.306 (4), c = 11.188 (9) Å, β = 92.86 (2)° at 298.1 K. For the room temperature phase III, smoothing equations are given to describe the thermal expansion.
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  • 87
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    Applied crystallography online 12 (1979), S. 615-615 
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    Notes: The low-temperature modification of (NH4)3In(SO4)3 is monoclinic, space group P21/c. The lattice constants are a = 8.963 (7), b = 15.644 (15), c = 9.131 (6) Å, β = 108.28 (5)° (Z = 4). The indexed powder diagram is given.
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  • 88
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    Applied crystallography online 12 (1979), S. 616-616 
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    Notes: Voglite, Ca2Cu(UO2)(CO3)4.6H2O (?) is monoclinic with a = 25.97, b = 24.50, c = 10.70 Å, β = 104.0°, Z = 16. Probable space group P21 or P21/m. Powder diffraction data are given.
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  • 89
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    Applied crystallography online 12 (1979), S. 617-618 
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    Notes: The ionic conductor N(CH3)4GeCl3 shows a phase transition at 424 K. The high-temperature modification is cubic with a = 6.552 (2)Å, space group Pm3m. At 293 K the compound is orthorhombic with unit-cell parameters a = 13.096 (2), b = 8.911 (1), c = 9.128 (2) Å, space group Pna21.
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  • 90
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    Applied crystallography online 12 (1979), S. 626-627 
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    Notes: The preliminary single-crystal data and powder pattern are given for a second polymorph of C.I. Pigment Red 1, C16H11N3O3. The powder pattern has been indexed using the single-crystal dimensions; the problems of multiple indexing have been reduced by comparison with single-crystal intensities.
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  • 91
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    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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  • 92
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    Applied crystallography online 14 (1981), S. 265-269 
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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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  • 93
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    Applied crystallography online 14 (1981), S. 274-279 
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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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  • 94
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    Applied crystallography online 14 (1981), S. 281-284 
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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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    Applied crystallography online 14 (1981), S. 285-290 
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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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  • 96
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    Applied crystallography online 14 (1981), S. 300-304 
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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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    Applied crystallography online 14 (1981), S. 315-320 
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    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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    Applied crystallography online 14 (1981), S. 329-336 
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    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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    Applied crystallography online 14 (1981), S. 348-349 
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    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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    Applied crystallography online 14 (1981), S. 352-353 
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