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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 307-310 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Transparent yellow-greenish single crystals of Pb6GeO8 were obtained by spontaneous crystallization from a melt with a molar ratio of PbO:GeO2 = 4.7:1. The compound is monoclinic, probable space group P21/a, a = 52.665 (12), b = 15.063 (4), c = 23.949 (6) Å and β = 111.03 (5)°; Dm(293 K) = 8.65 (3), Dx = 8.653 Mg m−3 for Z = 64 formula units. Pb11Ge3O17 was synthesized by sintering high-purity oxides PbO and GeO2 of molar ratio 3.69:1 at 990 K. The compound is also monoclinic, probable space groups C2/c or Cc, a = 25.117 (5), b = 15.440 (2), c = 45.529 (13) Å and β = 103.20 (4)°; Dm(293 K) = 8.55 (2), Dx = 8.560 Mg m−3 for Z = 32.
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  • 2
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 311-315 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Series of chalcopyrite-type solid solutions AgGaxIn1−xSe2 and CuGaxIn1−xSe2, 0≤x≤1, have been prepared by direct synthesis from the melt. The space group is I\bar 42d (No. 122), Z = 4. The unit-cell parameters a and c and the ratio c/a change linearly with x. Powder data at 298 K are given for AgGaSe2, AgGa0.80In0.20Se2, AgGa0.70In0.30Se2, AgGa0.40In0.60Se2, AgGa0.20In0.80Se2 and AgInSe2, and for CuGaSe2, CuGa0.60In0.40Se2, CuGa0.30In0.70Se2 and CuInSe2.
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  • 3
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 318-337 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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  • 4
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 338-339 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: If the length of the focal spot is increased while the width remains constant, X-ray output can be increased without changing the specific loading on the anode.
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  • 5
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 391-394 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: To increase the integrated reflexion intensity of a monochromating crystal, the strain distributed due to impurity introduction can be utilized and, compared with conventional mechanical processing, can be a more controllable method. From this viewpoint, numerical computations on the dynamical diffraction theory for distorted crystals have been performed for the 220 reflexion of Cu Kα X-rays by Si crystals with several different strain distributions; the one changing linearly with depth from −10−3 at the surface to zero at 28 μm depth gives the maximum integrated intensity within the restriction that the full width of the intensity profile is 100′′. The integrated intensity in this case is 5.3 and 4.5 times as strong as that of a perfect crystal plate for σ and π polarizations respectively. It is more enhanced for shorter wavelengths, e.g. nine times for Mo Kα. In addition, that intensity profiles for distributed strains are cut sharply at both ends is certainly favourable for the purpose of monochromating white X-rays. A preliminary experiment with an intentionally processed sample showed a fourfold intensity increase for a σ-polarized Cu Kα line with a full width of 80′′.
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  • 6
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 401-401 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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  • 7
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 88-92 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The device described here has been designed to perform microcreep experiments and, simultaneously, to get X-ray topographic images of the sample. Such dynamic experiments are now possible with white synchrotron radiation (LURE-DCI Orsay). The sample material, germanium, is hard to machine; so a simple shape was chosen (rectangular platelet 20 × 5 × 0–2 mm). The grip system is quite simple and the whole assembly is compact enough to be adapted to fit a standard goniometer head. Temperatures as high as 923 K in air and forces up to few tens of Newtons can be reached. The first experiments on Ge bicrystals have shown the device to perform as expected.
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  • 8
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 78-87 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A polished plate of type Ia natural diamond, containing regions which had been bombarded by electrons of energy between 2.0 and 4.5 GeV to total doses of 1̃024 electrons m−2 in polarized-photon production experiments, was examined, both before and after annealing at 1133 K for 8 h, using birefringence, cathodoluminescence photography and spectroscopy, X-ray topography and a novel method for mapping differences of interplanar spacing; `dilatation topography'. The annealing effected some reduction of overall strain, but it also generated an enhancement of diffraction contrast and cathodoluminescence at certain grown-in defects that the specimen contained. By means of dilatation topographs, interplanar spacings in a region of maximum electron-beam damage were compared with those in least-damaged regions some millimetres away. In the case of (110) planes that had been grazed by the electron beam, the maximum relative expansion, Δd/d, in damaged regions so found was reduced from 1.2 × 10−3 to 0.9 × 10−3 by the annealing. Evidence was obtained that the magnitude of expansion in the region of maximum damage was dependent upon crystallographic direction. Criteria are suggested for selection of diamonds to be used in polarized-photon production experiments.
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  • 9
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 93-95 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Cell data for monoclinic sebacic acid COOH(CH2)8COOH, C10H18O4, and dodecanedioic acid COOH(CH2)10COOH, C12 H22O4, are accurately given: (C10) a = 15.064 (6), b = 4.987 (4), c = 10.142 (6) Å, β = 133.14 (5)°; (C12) a = 17.594 (8), b = 4.933 (3), c = 10.174 (5) Å, β = 132.35 (3)°. It is shown that crystallographic data for molecular alloys [C10]x[C12]1 −x are significantly different for those prepared by fusion (m.a.f.) and those by sublimation (m.a.s.). X-ray powder data are given for the two series of solid solutions.
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  • 10
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 95-96 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The cell constants for the title compound, HMTSFT–CNQ4, (C12F4N4).(C12H12Se4), M.W. 748.21, were determined from a single crystal exposed on a Syntex P{\bar 1} automated diffractometer and then refined from precision powder data with Cr Kα1 (2.28962 Å): a = 21.906 (5), b = 12.918 (3), c = 4.0184 (10) Å and β = 91.658 (10)°; U = 1136.7 Å3, Z = 2, space group C2/m; Dc = 2.186 Mg m−3.
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  • 11
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 128-131 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A &psgr;-φ goniometer with two axes of rotation, driven by stepping motors, was designed as an attachment for a horizontal &thgr;/2&thgr; goniometer. By means of this arrangement it is possible to measure strains and compute stresses in single crystals and in separate crystals of a bicrystal or a coarse-grained polycrystalline specimen. The available rotations also make it possible to investigate residual macrostresses and textures in polycrystalline specimens. Results of the test measurements on a tensile specimen of a molybdenum single-crystal are given.
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  • 12
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 132-134 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A calculation of γ(r), the correlation function which gives the X-ray scattering of a cubic object of uniform density, is given for the full range of r. A new method, which can be applied to other systems, is used. The function γ(r) and its first derivative are everywhere continuous, but γ′′(r) is discontinuous at r = L and r = L□2 (L = cube edge length). This leads to an intersect distribution of unexpected shape. The scattering intensity as a function of angle is calculated by Fourier inversion of γ(r).
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  • 13
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 135-140 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An experimental method is described which enables the inelastically scattered X-ray component to be removed from diffractometer data prior to radial density function analysis. At each scattering angle an energy spectrum is generated from a Si(Li) detector combined with a multi-channel analyser from which the coherently scattered component is separated. The data obtained from organic polymers has an improved signal/noise ratio at high values of scattering angle, and a commensurate enhancement of resolution of the RDF at low r is demonstrated for the case of PMMA (ICI `Perspex'). The method obviates the need for the complicated correction for multiple scattering.
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  • 14
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 148-153 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Until now, the calculation of intensities diffracted by layer structures has only been treated in the two extreme cases, namely (i) the layers interfere completely and (ii) the layers do not interfere (turbostratic structures). The present paper develops the mathematical treatment which allows the calculation in the intermediate case, namely when layers are only partially interfering.
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  • 15
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 141-147 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A niobium tungsten bronze crystal with a nominal composition 3 Nb2O5.8WO3 gives circular diffuse scattering in the electron diffraction pattern. The diffuse rings change shape and size when the crystal is reduced at high temperature. The observations are explained by improving the cluster model proposed by De Ridder, Van Tendeloo, Van Dyck & Amelinckx [Phys. Status Solidi A (1977), 41, 555–560]; the present clusters are composed of nine pentagonal-tunnel sites. The 1 MV high-resolution electron microscope images reveal that the clusters have several different atomic arrangements and compositions. The relation between the clusters and the micro-domains, formed in the initial stage of long-range ordering, is clarified.
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  • 16
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 163-167 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Analysis of Bragg X-ray intensities collected on a single-crystal diffractometer with a pyrolitic graphite monochromator in the diffracted beam has revealed small systematic errors which are a consequence of the necessarily large illuminated area of monochromator crystal.
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  • 17
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 154-162 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The amount of information which can be obtained from a small-angle X-ray experiment can be considerably increased by orienting the solute particles with external forces during the scattering experiment. In this paper it is shown that orientation by flow, for instance through a capillary tube, gives additional information about size, shape, flexibility and rotational diffusion of the particles. The only requirement, in order to obtain flow-oriented samples, is that the solute particles must be relatively large and asymmetric. On the other hand, if the scattering curve is dependent on the flow rate through the capillary, it can immediately be concluded that the solute particles are asymmetric (or they are deformed in the hydrodynamic field). Equations describing the relationship between flow rate, molecular shape and scattered intensity are given, and theoretical intensity patterns for some representative cases are presented. It follows that there is a fundamental difference in scattering patterns for oblate and prolate ellipsoids of revolution. This difference can be used to differentiate between these two cases. Some experimental results obtained using inorganic model colloids are presented.
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  • 18
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 168-175 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An analysis of the small-angle scattering problem based on Shannon sampling is presented. It is shown that this approach leads to an accurate assessment of the information contained in a given data set and rigorous estimates of the errors inherent in the parameters derived therefrom.
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  • 19
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 401-402 
    ISSN: 1600-5767
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  • 20
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 605-607 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The crystal structure of Ta5P3 has been refined from Guinier–Hägg X-ray powder film data [Malmros & Thomas (1977). J. Appl. Cryst. 10, 7–11] using positional parameters from its structural isomorph Nb5P3 as starting values. The space group is orthorhombic Pnma (No. 62), with refined cell parameters a = 25.3210 (4), b = 3.4013 (1), c = 11.4614 (2) Å, V = 987.12 (5) Å3 and Z = 4. Final R = 4.9% [comparable with the R(F) of single-crystal work]. The structure exhibits the triangular prismatic Ta coordination about the P atoms and the dense packing of the Ta atoms, both familiar in many metal-rich phases formed between transition metals and non-metals of type P, As, S and Se.
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  • 21
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 611-611 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: In the paper Revised and new crystal data for indium selenides by Popovic, Tonejc, Grzeta-Plenkovic, Celustka & Trojko [J. Appl. Cryst. (1979), 12, 416–420] it was concluded that P6122 or P6522 was the probable space group of the second high-temperature, γ, phase of In2Se3. Also, in the paper Phases, lattice parameters and thermal expansion of (GaxIn1−x)2Se3, 1 ≥ x ≥ 0, between room temperature and melting point by Tonejc, Popovic & Grzeta-Plenkovic [J. Appl. Cryst. (1980), 13, 24– 30] the same space groups were suggested for the phase γ1, existing in the In-rich region. However, the space group in both cases should be P61 or P65. This is in agreement with the work of Likforman, Carré & Hillel [Acta Cryst. (1978), B34, 1 5] who solved the crystal structure of one of the forms of In2Se3, and with the work of Schulte-Kellinghaus & Krämer [Acta Cryst. (1979), B35, 3016 3017] who solved the crystal structure of AlInS3. Likforman, Carré & Hillel [Acta Cryst. (1978), B34, 1 5] call their phase the low-temperature form of In2Se3.
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  • 22
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 251-256 
    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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  • 23
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    Applied crystallography online 16 (1983), S. 276-276 
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    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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  • 24
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    Applied crystallography online 16 (1983), S. 277-277 
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    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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    Applied crystallography online 16 (1983), S. 284-284 
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  • 26
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    Applied crystallography online 16 (1983), S. 295-303 
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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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    Applied crystallography online 16 (1983), S. 317-324 
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    Topics: Geosciences , Physics
    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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  • 28
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    Applied crystallography online 16 (1983), S. 354-356 
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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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  • 29
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    Applied crystallography online 16 (1983), S. 357-357 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    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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    Applied crystallography online 16 (1983), S. 358-358 
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    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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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 508-511 
    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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  • 32
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    Applied crystallography online 16 (1983), S. 11-13 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    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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  • 33
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    Applied crystallography online 13 (1980), S. 340-341 
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  • 34
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    Applied crystallography online 13 (1980), S. 342-342 
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  • 35
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    Applied crystallography online 13 (1980), S. 354-358 
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    Notes: Image formation in a dispersive system, consisting essentially of a perfect cylindrically bent crystal in association with a point source, has been studied both for transmission and reflection. The Laue and Bragg conditions have been calculated together with the dispersive power. The treatment has been extended to include two crystals. In the single-crystal case and also for most versions of two-crystal combinations a point or line focus is required to obtain highly resolved spectra. A few versions of the two-crystal arrangement can be made to be focusing, thereby enabling the use of an extended radiation source.
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  • 36
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    Applied crystallography online 13 (1980), S. 364-367 
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    Notes: Zone-axis pattern maps for graphite have been obtained using multiple-micrograph montages. Maps have been constructed with bend-contour micrographs and with Kossel–Möllenstedt patterns, both obtained at 100 kV. The two kinds of map are compared.
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    Applied crystallography online 13 (1980), S. 385-390 
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    Topics: Geosciences , Physics
    Notes: Analytical explicit expressions have been derived for multiple-scattering effects under assumptions which are usually fulfilled in small-angle scattering. The expressions are used to evaluate quantitatively distortions of scattering patterns caused by multiple scattering. The distortions are discussed in terms of changes of the forward-scattering cross section, the radius of the gyration, the integrated intensity, the Porod region and Porod constant. In addition, the analytical expressions have been used to calculate the scattering cross section of the sample from scattering patterns which are strongly affected by multiple scattering.
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  • 38
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    Applied crystallography online 13 (1980), S. 401-401 
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  • 39
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    Applied crystallography online 13 (1980), S. 403-409 
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    Notes: The phases of ammonium nitrate, NH4NO3, doped with small amounts of NiO or CuO have been studied by X-ray and neutron diffraction at various temperatures from 80 to 423 K. NH4NO3 with metal-oxide additives, which are believed to form complexes, exists as a solid solution. Phase IV is stable down to 140 K in the NiO-doped samples and 210 K in the CuO-doped sample. The thermal expansion of this phase is extremely anisotropic, with the b axis expanding rapidly with increasing temperature while the a axis contracts slightly. At higher temperatures the doped samples transform directly from phase IV to phase II, bypassing phase III, starting at about 328 K. The structure of phase II, which is disordered, was refined in the space group P4/mbm. The structure of phase III contains hydrogen-bonded chains parallel to the b axis.
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  • 40
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    Applied crystallography online 13 (1980), S. 433-437 
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    Notes: A white-X-ray (Bremsstrahlung) four-circle diffractometer with a solid-state detector [Si(Li)] has been constructed. The system is operated by a small computer with magnetic disk memories, and enables energy-dispersive intensity measurements to be carried out with the X-rays selected from white X-rays. The present paper describes (1) how the present system can be used for energy-dispersive diffractometry even with the white radiation from a standard X-ray tube, and (2) how this system allows the measurement of the integrated intensities with almost the same accuracy as in angle-dispersive diffractometry with characteristic X-rays.
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  • 41
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    Applied crystallography online 13 (1980), S. 425-432 
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    Notes: A unique low-temperature, full-circle goniometer for single-crystal X-ray diffraction has been constructed with the novel adaptation of a closed-cycle refrigerator in such a manner that the cold finger remains stationary during the φ and χ rotations. This has been made possible through the development of a flexible heat-transfer link between the top of the φ shaft and the cold station. The new design concept incorporates several important features: (1) the vacuum shroud and radiation shields also remain stationary so as to reduce the X-ray windows to narrow slots; (2) the sample crystal is enclosed in a black, nearly isothermal cavity (Hohlraum); and (3) the φ shaft is mechanically decoupled from the thermal contraction of the cold finger and other parts. The new system has considerable advantages over presently existing low-temperature adaptations for X-ray diffraction: (1) the goniometer operates between 300 and 18 K without expenditure of liquid cryogen and with minimal attendance; (2) the system is capable of operating for long periods of time with minimal risk of interruption of the cooling cycle; (3) absorption of X-rays by the windows is minimal and independent of the Bragg angle; and (4) data collection at any temperature down to its present lowest limit of 18 K is virtually as easy as with any conventional room-temperature diffractometer. At the time of writing the instrument has been in use for over 10000 h and has measured over 100000 X-ray reflections from single crystals.
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    Applied crystallography online 13 (1980), S. 459-461 
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    Notes: A RAdial Distribution MOdeling Routine (RADMOR) is available which calculates directly the radial distribution function that would be obtained from electron, X-ray and neutron diffraction for spherical regions of known bonding topology. Crystalline as well as model fragment topologies can be evaluated in modeling the atomic arrangement in amorphous materials.
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  • 43
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    Applied crystallography online 13 (1980), S. 462-462 
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    Applied crystallography online 13 (1980), S. 465-471 
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    Notes: The performances of various optical elements are presented for ideally monochromatic X-rays in terms of position–angle space, which is used in the phase-space method. The optical elements discussed are a synchrotron radiation source, flat perfect crystals (reflection and transmission geometries), mosaic crystals, curved crystals of reflection (Johansson, Johann and logarithmic spiral types) and transmission geometries, and an elliptic total reflection mirror. The angular widths of acceptance and emergence for diffraction are properly taken into account in both the flat and curved crystals. It is shown that focusing optical elements such as a curved crystal and an elliptical mirror should not be treated simply as lenses.
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    Applied crystallography online 13 (1980), S. 486-493 
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    Notes: Both superlattice and fundamental reflections have been used in an X-ray determination of the vanadium-atom displacements induced by selected ordering of interstitial deuterium in a multi-domain crystal of V2D. The magnitudes of these displacements along X and Z directions of the pseudo-tetragonal (b.c.t.) unit cell are designated DAX and DAZ respectively, where Z is along the tetragonal c axis. Measurements of the lattice parameters yield DAX ∼0.03 and DAZ ∼0.17 Å. From intensity measurements, the best values for the displacements are DAX = 0.03±0.01 and DAZ = 0.15±0.02 Å, and the purely thermal Debye–Waller factor was found to be 2B = 0.025 Å2. The temperature dependences of both the long-range-order parameter, S, and the lattice parameters of the b.c.t. unit cell were also investigated. Both verify that the phase transition from β (monoclinic) to α (b.c.c.) is first order in character with no intervening ε (tetragonal) phase as in V2H. There is additional evidence that the disordering process includes random occupancy of both Z octahedral and random tetrahedral sites.
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    Applied crystallography online 13 (1980), S. 505-512 
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    Notes: One lamellar phase, observed in the mitochondrial lipids–water system at low temperature (ca 253 K) and at low water content (ca 15%), contains four lipid monolayers in its unit cell, two of type α and two of type β. Previous X-ray scattering studies of this phase led to an ambiguity: the phase could contain either two homogeneous bilayers, one α and one β, or two mixed bilayers, each formed by an α and a β monolayer. A solution to this problem was sought in a neutron scattering study as a function of the D2O/H2O ratio. Because of limited resolution, straightforward analysis of the neutron scattering data leads also to ambiguous results. Using a more sophisticated analysis based upon the zeroth- and second-order moments of the Patterson peaks relevant to the exchangeable components, it is shown that the weight of the evidence is in favour of a structure containing mixed bilayers.
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    Applied crystallography online 13 (1980), S. 529-532 
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    Notes: At the IA magnetic transition (12.5 K) in CeBi a theoretical study has suggested that either the Ce or Bi sublattices should move with respect to the other. Such a distortion would give rise to extra reflections of the form 0′0′l+½. A search for such a reflection using a Bond X-ray diffraction technique was conducted. The 007½ line was not found and an upper limit of 2̃ × 10−4 was set for the magnitude of the expected internal distortion. This limit is valid for a surface layer whose thickness equals the penetration depth of the X-radiation which is about 0.4 × 10−2 mm.
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  • 48
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    Applied crystallography online 16 (1983), S. 577-578 
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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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    Applied crystallography online 16 (1983), S. 580-580 
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    Applied crystallography online 16 (1983), S. 581-589 
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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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    Applied crystallography online 16 (1983), S. 611-622 
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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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    Applied crystallography online 16 (1983), S. 623-628 
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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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    Applied crystallography online 16 (1983), S. 641-644 
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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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    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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    Applied crystallography online 16 (1983), S. 649-649 
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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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    Applied crystallography online 16 (1983), S. 658-659 
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    Applied crystallography online 16 (1983), S. 653-657 
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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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    Applied crystallography online 16 (1983), S. 99-102 
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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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    Applied crystallography online 16 (1983), S. 96-98 
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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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    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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    Applied crystallography online 16 (1983), S. 136-137 
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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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    Applied crystallography online 16 (1983), S. 142-143 
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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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    Applied crystallography online 16 (1983), S. 144-150 
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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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    Applied crystallography online 16 (1983), S. 143-143 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    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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    Applied crystallography online 16 (1983), S. 157-158 
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    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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    Applied crystallography online 16 (1983), S. 192-197 
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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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    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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    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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    Applied crystallography online 16 (1983), S. 257-258 
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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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    Applied crystallography online 16 (1983), S. 259-263 
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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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    Applied crystallography online 16 (1983), S. 270-273 
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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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    Applied crystallography online 16 (1983), S. 279-281 
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    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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    Applied crystallography online 16 (1983), S. 281-283 
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    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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    Applied crystallography online 16 (1983), S. 289-294 
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    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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    Applied crystallography online 16 (1983), S. 309-316 
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    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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    Applied crystallography online 16 (1983), S. 325-340 
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    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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    Applied crystallography online 16 (1983), S. 357-357 
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    Notes: Corrections to a paper by Schoenlein, Hobbs & Heuer [J. Appl. Cryst. (1980), 13, 375–379] are given.
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    Applied crystallography online 16 (1983), S. 360-360 
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    Applied crystallography online 16 (1983), S. 360-361 
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    Applied crystallography online 16 (1983), S. 361-361 
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    Applied crystallography online 16 (1983), S. 384-389 
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    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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    Applied crystallography online 16 (1983), S. 390-398 
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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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    Applied crystallography online 16 (1983), S. 407-414 
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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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    Applied crystallography online 16 (1983), S. 420-427 
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    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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    Applied crystallography online 16 (1983), S. 430-430 
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    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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    Applied crystallography online 16 (1983), S. 438-438 
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    Applied crystallography online 16 (1983), S. 449-452 
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    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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    Applied crystallography online 16 (1983), S. 473-478 
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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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    Applied crystallography online 16 (1983), S. 479-485 
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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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    Applied crystallography online 16 (1983), S. 512-518 
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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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    Applied crystallography online 16 (1983), S. 524-531 
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    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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    Applied crystallography online 16 (1983), S. 532-534 
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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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    Applied crystallography online 16 (1983), S. 572-573 
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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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    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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  • 96
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 576-576 
    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.
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  • 97
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 580-580 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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  • 98
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 580-580 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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  • 99
    Electronic Resource
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 599-605 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A method of measuring the difference between the lattice parameter of a region of an unknown sample and that of a region of a standard reference crystal to a sensitivity of 1 part in 109 is presented. Problems inherent in multiple-beam arrangements due to sample strains and non-uniformity have been overcome by the use of a new double-source arrangement in which the two X-ray beams sample the same spot on a crystal under study. Ways of identifying and preventing errors from significant mechanical and thermal effects arising in the sensitivity region explored are indicated.
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  • 100
    Electronic Resource
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 637-640 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A qualitative and quantitative morphological study on the α and β phases of ammonium pentaborate tetrahydrate has been carried out. Crystals of the two phases were obtained by slow evaporation from aqueous solutions. Usually the α phase was obtained with {101}; {\bar 101}; {011} and {110} as crystal forms, a high percentage of the crystals (99%) were twins, with a twofold axis parallel to c as the twin law. When MgCl2.6H2O was added to the solution, the β phase was obtained as prismatic crystals elongated along [\bar 110] with {111}, {\bar 111 } and {001} as crystal forms. Generally, these crystals were also twins, with a twofold axis parallel to [110] as twin law. A qualitative and quantitative morphological study showed the α-phase crystals to have the theoretical growth forms, while the crystal forms of the β phase were explained by the presence in the solution of (H2O)6Mg2+ and Cl− ions.
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