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  • International Union of Crystallography (IUCr)
  • 1980-1984  (5,963)
  • 1965-1969  (2,736)
  • 1940-1944
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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 1-19 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The desirability and requirements for a specimen capable of testing the resolving power and other image characteristics of an electron microscope are discussed in detail. In this discussion, the underlying diffraction phenomena are particularly utilized. A partially graphitized carbon black is shown to satisfy the requirements extremely well and constitutes an easily prepared specimen for conducting tests of image quality in the molecular size range. The structure of the test object is known in detail with the result that readily interpretable phase contrast images are obtained. Micrographs illustrating the use of the 3.4 Å (002) spacing for magnification calibration, astigmatism and asymmetry check as well as resolving power are exhibited. The second order c-spacing of 1.7 Å is occasionally found in an image. The micrographs shown herein were taken with two different electron microscopes by different operators obtaining the same structural detail in the images. It is concluded that the carbon black test object offers the best possibilities for evaluating image performance of any specimen yet suggested.
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  • 2
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 84-90 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Bent-glass mirrors can be used to produce a narrow, highly collimated X-ray beam, particularly suitable for photographing diffraction patterns from crystals with very large unit cells (i.e., several hundred Å to a side). A camera is described that employs double-mirror focusing optics with a precession apparatus. A comparison of optical reflection and simple collimation shows that for high resolving power, focusing devices are very much superior to pinhole collimators. The reduction of background is especially noteworthy. Use of this camera has permitted the collection of accurate three-dimensional data from crystals of tomato bushy stunt virus.
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  • 3
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 121-122 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A new method for determination of the polarization factor of a crystal monochromator is presented. This method is based on the use of polarized X-rays produced by anomalous transmission or the Borrmann effect. The polarization factors of two quartz (10\overline 11) monochromators of Johansson type have been measured with Cu Kα radiation, and the resulting values are in close agreement with the expression derived from the kinematic diffraction theory.
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  • 4
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 126-128 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An adapter which supports a Polaroid flat-plate film holder has been designed for a standard Weissenberg goniometer. A number of applications, including a method for rapidly aligning single crystals, are described.
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  • 5
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 145-153 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The use of X-ray diffraction topography to identify domains of different polytype in crystals of silicon carbide has been described in a previous paper. Further methods have been developed and applied to the analysis of thin films deposited epitaxically from the vapour phase onto basal surfaces of crystals of hexagonal α-SiC. The epitaxic films consist either of α-SiC, or of the cubic form β-SiC, with multiple twinning about the axis normal to the surface. The fine scale texture of interlocking twin domains is readily demonstrated in X-ray diffraction topographs.
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  • 6
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 165-171 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Inversion twin boundaries in BeO crystals (wurtzite structure) can be studied by X-ray topography. They can be regarded as a special kind of stacking fault. The section topograph images of a twin boundary, lying parallel to the c axis, agree well with the theory for a single stacking fault. From the contrast variation of the images for various reflections, it is concluded that the oxygen sublattice on one side of the twin boundary is displaced from that on the other side by \mid(1/16)[001]\mid so that the oxygen layer parallel to the basal plane on one side is located at the center of the oxygen and beryllium layers on the other side. The image contrast in section topographs is very sensitive to the phase shift due to a fault. The phase shift of a few degrees can be detected easily. This sensitivity leads to an accurate structure determination of the inversion twin boundary.
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  • 7
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 181-184 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The refractive index, n, for X-rays is measured by interposing a prism in the path of X-rays falling on a perfect silicon crystal at the Bragg incidence angle. Owing to the deviation angle of the prism, the separation of the two wave fields excited in the silicon crystal is modified, from which the value of n − 1 can be deduced with a 1% accuracy. The method has been applied to the measurement of the anomalous dispersion correction for the refractive index of zirconium for Mo Kα.
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  • 8
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 187-189 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A method based on the variation of the lattice parameter with Li content, for the quantitative determination of lithium in the system Lix+Ni1−2x2+Nix3+O2−, is proposed. A precision between 1 and 5% relative, depending upon the concentration range, has been obtained. The results are compared with those obtained by flame emission spectroscopy. For values of x 〉 0.12 the original rhombohedral lattice transforms into a face centred cubic lattice.
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  • 9
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 198-198 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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  • 10
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 139-145 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A study of strain inhomogeneities in a zone-refined tungsten crystal oriented for (123) slip was carried out before and after a slight compression. The study was based on changes of interplanar spacings measured along different crystallographic directions and samples from different areas of the crystal by means of the X-ray back-reflection divergent beam method. Upon compression a redistribution of the locked-in elastic strains took place and the induced strains assumed a more homogeneous distribution for one of the sets of (123) planes considered. This homogeneity in the strain distribution along definite crystallographic directions is believed to result from the interaction of the primary slip dislocations with the pre-existing dislocation configuration and appears to be characteristic of the initial stage of work-hardening. The dislocation interaction induced by a small strain found practical application in the elimination of a troublesome substructure in highly zone-refined tungsten crystals and appears to form the scientific basis of certain stress-relief treatments long practised in metallurgical technology.
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  • 11
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 218-226 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: All the hard carbons are composed of three phases when they are heated above 2000°C: non-graphitizable carbon, graphitizable carbon, and graphite (the latter two appearing only in very small amounts). When the heat treatment temperature is increased to 3000°C, these phases change in various ways. At low temperatures, the non-graphitizable phase is formed by small turbostratic stacks of carbon layers which are oriented completely at random inside the carbon grains. Above 2000°, these stacks begin to undergo mutual rearrangement to produce small fibers by ordering roughly parallel to each other. The graphitizable phase is formed of spheres made up of conical rolled spirals, which are themselves made up by turbostratic stacking of the carbon layers. When heat treated, each sphere transforms to graphite very suddenly. The third phase is well crystallized graphite with stacking faults and twist defects.
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  • 12
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 241-246 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Samples in the Bi–Te system containing 59.0, 58.0, 57.0, 55.0, 51.0, and 50.0 at.% Te, in addition to 5 samples within the Bi2Te3 homogeneity range, have been equilibrated near 525 or 450°C and room temperature powder diffraction patterns taken. There are now 4 known phases in the 50–60 at.% Te region. The 59.0 and 58.0 at.% samples are two phase at 525°C. The 57.0 and 55.0 at.% samples are new phases with hexagonal parameters, a = 4.4106±0.0002 Å, c = 54.330±0.003 Å and a = 4.4214±0.0004 Å, c = 78.195±0.012 Å, respectively. The 51.0 and 50.0 at.% samples are two-phase at 525 C. At 450°C the 51.0 at.% sample is single phase while the 50.0 at.% sample probably is not. The common indexing scheme for the 50.0 and 51.0 at.% samples is different from those for the 55–0 and 57.0 at.% samples. For the 51.0 at.% sample a = 4.4296±0.0002 Å and c = 24.017±0.001 Å. The 00l lines for all these phases vary strongly with composition and those near d = 9 and 5 Å are isolated enough to provide a convenient way of distinguishing among the various phases. The results are discussed in terms of other phase-diagram information. They are inconsistent with Stasova's correlation between composition and powder-pattern indices for the Bi–Te, Bi–Se, and Sb–Te systems.
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  • 13
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 262-262 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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  • 14
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 263-271 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The study of the scattering outside the Bragg reflexions shows no local order in the ordered phase I of alloys such as Au (50 at. %) Cu (46 at. %) Ni (4 at. %) even for the smallest degree of long range order. The modulation of the scattering appears only with the presence of short range order in the disordered α phase. There is evidence of a two-phase region on the equilibrium diagram at the AuCu3 stoichiometric composition.
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  • 15
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 290-292 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Accurate lattice parameters (at 25 and 48°C), density, thermal expansion coefficients, the indexed powder pattern, and optical data are given for Ba(4+x)Na(2−2x)Nb10O30, where x = 0.13±0.013, grown by pulling from a nominally stoichiometric melt.
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  • 16
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 313-317 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: In an earlier communication by the authors it was shown that the stack height distribution in a raw carbon black followed an exponential law. Extension of these studies to a heat-treated (2000°C) black showed that the exponential law is still valid when stacking is extensive. The exponential law and the effect of heat-treatment are explained by the existence in blacks of extensive stratification rather than the presence of short stacks of small layers. Evidently heat-treatment results in annealing of the strata to yield uniform layer domains and more ordered stacking. Simple expressions are derived for calculating the profiles of the 00l reflections and the coefficient of the exponent.
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  • 17
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 324-325 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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  • 18
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 1 (1968), S. 323-323 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Long chain secondary ammonium chlorides, bromides and iodides crystallize in a preferred orientation. Values of the basal spacings of the salts indicate hydrocarbon chains oriented towards each other between planes of the ionic heads. The inclination angle of the chains was found to be 40°.
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  • 19
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 72-76 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The paper describes a method for obtaining consistent estimates of domain size from an evaluation of coefficients derived from curves fitted to the tails of diffraction profiles. An estimate of the mean domain size is computed directly from the intensity data and this is equivalent to the value derived from the slope of the variance-range function. For many applications this provides a convenient alternative to the method described by Langford & Wilson (Crystallography and Crystal Perfection. London: Academic Press, 1963) but does not replace it. An advantage of the present method is its simplicity and consequent reduction in computing time. It is easier to apply if a computer is not available and is applicable in cases where one or other of the profile tails overlaps that of a neighbouring line. The results obtained by this method are comparable in accuracy to those given by existing techniques.
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  • 20
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 18-24 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The usual method of specimen preparation for electron-probe microanalysis can introduce errors of up to about ±3% in the estimates of the amount of an element present. It is believed that these errors are caused by the formation of `flowed' layers on the surfaces of polished samples. Two methods of reducing the errors are described.
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  • 21
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 30-36 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The lattice constants and the atomic position parameter, z, of a high purity, low strain, single-crystal of arsenic have been determined. Low extinction reflections of filtered Mo Kα and Ag Kα radiation were used for the determination of z. The Bond precision technique with Mo Kα radiation was used for the determination of the unit-cell dimensions a and c. Average values for a and c in Å, and for z are: 4.2°K z = 0.22764 a = 3.7597 c = 10.4412; 78°K z = 0.22754 a = 3.7595 c = 10.4573; 299±3°K z = 0.22707 a = 3.7598 c = 10.5475. The estimated standard deviation of z is ±0.00004 at 4.2°K, ±0.00002 at 78°K and ±0.00005 at 299°K. The precision of a is estimated to be ±0–0001 Å and that for c to be ±0.0002 Å. The results for As are compared with those reported earlier for Sb and Bi.
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  • 22
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 146-147 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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  • 23
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 156-164 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The strain induced phase transformations produced in lead monoxide powders by ball milling at temperatures ranging from −196 to 200°C have been studied by X-ray diffraction methods. It has been found that either of the two polymorphs, litharge and massicot, was partially converted to the other at all the temperatures investigated, and that, whichever polymorph was the starting material, the end product, after a sufficiently long time, was a mixture of the two polymorphs, both highly strained. The percentage of each phase present was found to be dependent on the temperature of deformation. The results have been interpreted by consideration of the production of the microstrain energy required to overcome the energy barrier to the transformation, and of the shear generated in the mill on the pressure-temperature phase diagram. It is considered that shear stresses can affect the nature of the pressure-temperature phase diagram, in a manner theoretically postulated by Kumazawa. The commercial importance of the results has been briefly outlined.
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  • 24
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 176-180 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The theory of the direct comparison X-ray method of phase analysis is extended to correct for preferred orientation effects. Texture parameters are defined to assess the type and intensity of preferred orientation using data from diffractometer patterns. The analysis is illustrated with results obtained on three austenitic stainless steels.
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  • 25
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 192-192 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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  • 26
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 200-209 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A method is presented which combines the analysis of X-ray absorption profiles and selected area X-ray topographs. The method is based on X-ray divergent beam patterns obtained in transmission. The absorption profiles are obtained by unfolding the spectral distribution from the profiles of the deficiency conics, whereas the selected area topographs derive from the corresponding diffraction conics. The synergy of the two techniques makes the method particularly useful for the elucidation of anisotropic effects and inhomogeneities of defect structures. An example is given for the room temperature deformation of beryllium.
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  • 27
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 223-230 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An X-ray reflexion topography camera has been designed to study structural defects near the surface of monocrystalline semiconductors. Large surfaces can be covered by means of successive fixed exposures. A surface of 30 mm x 10 mm for example can be studied in less than ten minutes on nuclear emulsions. The conditions for the observations of dislocations in gallium arsenide have been examined: the choice of reflecting planes is limited by the depth of penetration of X-rays, so that the effective crystal thickness must be of the order of the width of a dislocation image (2-5 microns). Studies to which these observations can be applied are numerous: structural defects induced by diffusion, lattice strains, orientation of dislocations near the surface, structural evolution of silicon during integrated circuits elaboration, structure of cleavage surfaces, lapping and polishing defects, structural defects of epitaxic layers.
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 234-234 
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  • 29
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 236-236 
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  • 30
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    Applied crystallography online 2 (1969), S. 249-252 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The practical importance of tungsten monocarbide prompted an investigation into its wear mechanism. Initial studies on ball-milled tungsten carbide powders revealed considerable plastic deformation, coupled with a reduction in crystallite size. Deformation stacking faults, involving slip on the basal plane, were observed. The work was extended to sintered blocks, tool tips and single crystals. Studies on the worn surfaces of these revealed plastic deformation that extended to a depth of a few microns below the surface. The plastic deformation is an important factor in the wear of tungsten carbide.
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  • 31
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    Applied crystallography online 2 (1969), S. 295-297 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A method is suggested which allows several independent determinations of the rhombohedral angle using data from a single diffraction pattern. This is applied to the intermetallic compound SbSn.
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  • 32
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    Applied crystallography online 2 (1969), S. 297-300 
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    Notes: The Hankel transform method proposed by Fedorov & Aleshin (1966; Vysokomol. Soed. 8, 1506; English translation, 1967: Polymer Science USSR 8, 1657) for calculating the electron density of long cylindrical particles with circular cross section is tested with theoretical intensity functions for which the density can be found both by an exact calculation and by numerical integration. (In this method, the density is assumed to depend only on the distance from the cylinder axis.) The tests show how the degree of resolution obtained in the density curve is related to the largest scattering angle at which data are available. For the step function density corresponding to a cylinder with uniform electron density, the requirements are more severe than for continuously decreasing density functions. The possibility of obtaining useful results with the available scattering data from two biological macromolecules is discussed.
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  • 33
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 247-248 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A previously given analysis of the beam and specimen tilt errors in the Bond single-crystal method of lattice parameter determinations is extended to give a simple generalized treatment. This shows that the error passes through a maximum in accordance with an empirical observation by other workers. Crystal alignment procedures are examined in the light of the results.
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  • 34
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    Applied crystallography online 2 (1969), S. 259-261 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A storage oscilloscope has been attached to the IBM 1800 computer that is used for pole-figure data acquisition. It allows fast plotting of pole figures by modulation of the cathode ray beam according to the pole density as it scans the stereographic projection along a spiral path. The time needed to plot the pole figure is reduced by a factor of eight as compared with a mechanical plotter.
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  • 35
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 2 (1969), S. 281-288 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The axial thermal expansion of monoclinic and tetragonal ZrO2 and of monoclinic HfO2 was studied over the temperature range from room temperature to 1400 °C. The linear thermal expansion coefficients were calculated. Thermal expansion along (x 106 per °C) a = 10.31 monoclinic ZrO2, 11.60 tetragonal ZrO2, 9.34 monoclinic HfO2; b = 1.35 monoclinic ZrO2, – tetragonal ZrO2, 2.98 monoclinic HfO2; c = 14.68 monoclinic ZrO2, 16.08 tetragonal ZrO2, 13.10 monoclinic HfO2. Some aspects of the present study, such as anisotropy of thermal expansion and a pretransformation vibrational anomaly, are discussed briefly.
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  • 36
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 307-310 
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    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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  • 37
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    Applied crystallography online 13 (1980), S. 311-315 
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    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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  • 38
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    Applied crystallography online 13 (1980), S. 318-337 
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  • 39
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    Applied crystallography online 13 (1980), S. 338-339 
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    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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  • 40
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    Applied crystallography online 13 (1980), S. 391-394 
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    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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  • 41
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    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 401-401 
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  • 42
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    Applied crystallography online 13 (1980), S. 88-92 
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    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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  • 43
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    Applied crystallography online 13 (1980), S. 78-87 
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    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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  • 44
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    Applied crystallography online 13 (1980), S. 93-95 
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    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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  • 45
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    Applied crystallography online 13 (1980), S. 95-96 
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    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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  • 46
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    Applied crystallography online 13 (1980), S. 128-131 
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    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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  • 47
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    Applied crystallography online 13 (1980), S. 132-134 
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    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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  • 48
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    Applied crystallography online 13 (1980), S. 135-140 
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    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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  • 49
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    Applied crystallography online 13 (1980), S. 148-153 
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    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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  • 50
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    Applied crystallography online 13 (1980), S. 141-147 
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    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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  • 51
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    Applied crystallography online 13 (1980), S. 163-167 
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    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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  • 52
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    Applied crystallography online 13 (1980), S. 154-162 
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    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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  • 53
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    Applied crystallography online 13 (1980), S. 168-175 
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    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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  • 54
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    Applied crystallography online 14 (1981), S. 3-7 
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    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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    Applied crystallography online 14 (1981), S. 24-27 
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    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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    Applied crystallography online 14 (1981), S. 43-50 
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    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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  • 57
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    Applied crystallography online 14 (1981), S. 60-61 
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    Notes: A fitting method is proposed for X-ray diffraction profiles which requires only a small number of parameters.
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    Applied crystallography online 14 (1981), S. 61-62 
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    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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    Applied crystallography online 14 (1981), S. 64-65 
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    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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    Applied crystallography online 14 (1981), S. 68-68 
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    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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    Applied crystallography online 14 (1981), S. 85-93 
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    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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    Applied crystallography online 14 (1981), S. 124-130 
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    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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    Applied crystallography online 14 (1981), S. 117-123 
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    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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    Applied crystallography online 14 (1981), S. 137-139 
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    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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    Applied crystallography online 14 (1981), S. 139-141 
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    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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    Applied crystallography online 14 (1981), S. 145-148 
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    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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    Applied crystallography online 14 (1981), S. 151-153 
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    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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  • 68
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    Applied crystallography online 14 (1981), S. 160-168 
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    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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  • 69
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    Applied crystallography online 13 (1980), S. 401-402 
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  • 70
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    Applied crystallography online 14 (1981), S. 370-382 
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    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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  • 71
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    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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  • 72
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    Applied crystallography online 14 (1981), S. 432-436 
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    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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  • 73
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    Applied crystallography online 14 (1981), S. 444-446 
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    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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  • 74
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    Applied crystallography online 14 (1981), S. 455-461 
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    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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  • 75
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    Applied crystallography online 14 (1981), S. 465-465 
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    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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  • 76
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    Applied crystallography online 14 (1981), S. 491-491 
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    Applied crystallography online 15 (1982), S. 5-14 
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    Notes: A method of measuring accurate cubic lattice parameters is developed which is suited to the type of conditions encountered in high- and low-temperature powder diffractometry. This is based on the fact that the absolute Bragg angle of each line in an indexed cubic diffraction pattern can be determined from a knowledge of the differences in angles between lines. Accurate zero-angle alignment, therefore, is unnecessary. Furthermore, it is shown that the peak or centroid shift of the line profiles arising from the instrumental and physical aberrations can be determined directly from the measured angular data without assuming a specific angular dependence. In practice the accuracy of the method is of the order of 0.0002 Å for a lattice parameter of approximately 8 Å.
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    Applied crystallography online 15 (1982), S. 20-26 
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    Notes: Calculations of diffraction line profiles and Scherrer constants for crystallites whose external shape has cubic symmetry are extended to crystallites of cylindrical shape. The analysis includes the limiting cases of acicular crystals and disks and, to a reasonable degree of approximation in many cases, to hexagonal prisms. These shapes have applications in size determination for materials which form prismatic crystallites, particularly those which belong to the hexagonal system or have been derived from substances with this symmetry.
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    Applied crystallography online 15 (1982), S. 35-38 
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    Notes: The Warren–Averbach profile analysis was modified to study the deformed state of Al. The X-ray diffraction effect of dislocations locating on cell boundaries may be treated as `size broadening', while that of dislocations inside cells is `strain broadening', which may be treated with Wilkens's theory. X-ray Debye profile measurement was performed on deformed, recovered and annealed samples of commercial pure Al. Some information concerning the dislocation glide systems and distribution as well as the differences between the deformed and recovered state were given by the Debye profile analysis. The results are in good agreement with those obtained by other authors, which prove the reliability and correctness of the method.
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    Applied crystallography online 15 (1982), S. 39-47 
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    Notes: The extended structure of the Pt L3 X-ray absorption edge for some platinum compounds was measured and Fourier inverted. It is shown that the way in which the contribution of the isolated atom is subtracted from the absorption spectrum may influence the shape of the first peak in the Fourier transform and possibly lead to erroneous structural interpretations concerning the first-neighbour shell of the absorbing atom. These errors are the more important the smaller the separation between the absorbing atom and its nearest neighbours. An improved method of subtraction of the isolated-atom absorption is proposed and checked.
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    Applied crystallography online 13 (1980), S. 605-607 
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    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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    Applied crystallography online 13 (1980), S. 611-611 
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    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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    Applied crystallography online 15 (1982), S. 251-254 
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    Notes: Changes in the microporosity of several types of Brazilian high-ash coals have been analyzed by small-angle X-ray scattering as a function of thermal treatment. Pore size, determined using Guinier plots, decreased following thermal treatment of the samples. The modification of porosity induced by thermal treatment was similar for high-ash and low-ash coals, from which it may be inferred that mineral content is not a determining factor in the process of pore formation. Internal surface area for the samples was calculated with SAXS data. A correlation is established between the internal surface area values obtained and the carbon content and heat-treatment temperatures of the samples.
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    Applied crystallography online 15 (1982), S. 279-281 
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    Notes: Crystal data for the series of piperazinium bis(n-alkanoates) of the type 2[CxH2x − 1O2−] [C4H12N22+] for x = 1 to 16 are presented. Most of these compounds have triclinic unit cells whose dimensions, obtained from single-crystal work, have been used to index their powder diagrams. The a ({\bar a} = 5.718 Å) and b ({\bar b} = 7.481 Å) cell dimensions remain nearly constant while the c dimension and the volume of the unit cell increase linearly with x, the number of carbon atoms in the alkanoate anion. Presumably the aliphatic sequence in the alkanoate anion adopts the fully extended conformation and lies in the bc plane and nearly along the c direction.
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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 15 (1982), S. 461-462 
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    Notes: Lattice-constant thermal expansions, Δa/a and Δc/c, have been measured on α-HgI2 single crystals from 293 K up to the red-to-yellow transition temperature. The curves Δa/a(T) and Δc/c(T) are linear. The thermal expansion coefficients are determined: α[100] = (1.0 ± 0.1) × 10−5 K−1 and α[001] = (4.6 ± 0.1) × 10−5 K−1. No evidence of a red-to-orange phase transition could be found.
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    Applied crystallography online 15 (1982), S. 452-460 
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    Notes: Total neutron scattering data were collected on sputtered YFe2 at 298 K and TbFe2 at 423 K with a wavelength of 0.7 Å. The TbFe2 data were collected above the magnetic ordering temperature of 383 K. In addition, the elastic neutron scattering of TbFe2 was measured with the use of a pyrolytic graphite analyzer at a wavelength of 1.5 Å, and its total X-ray scattering was measured with Mo radiation and a silicon-lithium drifted detector. Experimental radial distribution functions, with statistical error limits, were calculated. Errors due to an incorrect background, scaling of the data and termination effects were minimized. The scale and shape of the experimental background and the coordination numbers, internuclear distances and disorder parameters, for the first six coordination spheres, have been determined. The contribution of paramagnetic inelastic scattering from TbFe2 to the total neutron scattering is quite appreciable. The shape of the background scattering, which goes through a maximum, is indicative of residual coherence and suggests short-range magnetic ordering where neighboring atom spins are aligned. These effects are not observed in YFe2, nor in the elastic TbFe2 data. The metallic glasses have a structural topology which is quite different from that found in their crystalline analogues. The transition-metal substructure, consisting of corner-sharing tetrahedra, is the only aspect of the crystalline topology preserved in the amorphous phase. The structural parameters suggest a tendency of the rare-earth atoms to cluster, thereby decreasing the number of Fe nearest neighbors relative to the crystalline structure.
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    Applied crystallography online 15 (1982), S. 55-59 
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    Notes: By using data from the Wallace & Ward [J. Appl. Cryst. (1975), 8, 255–260] cylindrical texture camera integrated with other traditional X-ray powder film techniques for very low and very high diffraction angles, a new high-temperature modification of CeO2 was identified and indexed resulting in a trigonal or hexagonal unit cell with a = 8.36(2) and c = 10.42(2) Å, (axial ratio 1.264) and Z = 16. The new phase is an oxidation product of CeO2-doped hot-pressed silicon nitride. It can be quenched to room temperature under appropriate conditions. Its stability on reheating is strictly related to its interaction with the silicate phase.
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    Applied crystallography online 15 (1982), S. 60-64 
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    Notes: Multiple electron scattering between weak beams has been used as the basis for a simple method to determine the absolute polarity of some non-centrosymmetric crystals. For crystals with the sphalerite structure many orientations have been found in which small departures from centrosymmetry produce large effects on the convergent-beam diffraction patterns (microdiffraction). The effects are reasonably independent of thickness and so can be analyzed qualitatively without the use of computers.
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    Applied crystallography online 15 (1982), S. 570-571 
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    Notes: A method is proposed for unambiguously indexing X-ray multiple diffraction patterns obtained with irregularly shaped crystals on a four-circle diffractometer. The method is derived from the orientation matrix together with the operation of crystal rotation. It is shown that this method facilitates the procedures in the experimental method for phase determination.
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    Applied crystallography online 15 (1982), S. 574-576 
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    Notes: Unit-cell constants for synthetic fluoroalleghanyite compounds have been determined by the refinement of X-ray powder diffraction data. Manganese norbergite: Pbnm, a = 4.862(2), b = 10.797(3), c = 9.188(2) Å, U = 482.4(4) Å3, Z = 4; alleghanyite: P21/b, a = 4.871(2), b = 10.818(6), c = 8.206(5) Å, α = 108.58(5)°, U = 414.1(7) Å3, Z = 2; manganhumite: Pbnm, a = 4.888 (2), b = 10.712(2), c = 21.749(6), U = 1138.8(5) Å3, Z = 4; sonolite: P21/b, a = 4.889(1), b = 10.668(3), c = 14.239(5), α = 100.83(5)°, U = 731.9(5) Å3, Z = 2. The JCPDS Powder Diffraction File numbers are: for manganese norbergerite 33–1500; for alleghanyite 33–1499; for manganhumite 33–1498; for sonolite 33–1497.
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    Applied crystallography online 15 (1982), S. 577-577 
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    Applied crystallography online 15 (1982), S. 577-578 
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    Applied crystallography online 15 (1982), S. 579-579 
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    Applied crystallography online 15 (1982), S. 579-580 
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    Applied crystallography online 15 (1982), S. 116-119 
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    Notes: Three members of a new family of phases, Li3Mg2XO6: X = Nb, Ta, Sb, have been prepared by solid-state reaction of MgO and Li3XO4. Unit-cell parameters of Li3Mg2TaO6 determined by electron diffraction and refined by X-ray powder diffraction are a = 8.883(2), b = 5.802(2), c = 17.437(6) Å, with space group Fddd; z = 8. Powder diffraction data of Li3Mg2NbO6 and Li3Mg2SbO6 were indexed by analogy with those of Li3Mg2TaO6 and unit-cell dimensions obtained by least-squares refinement: Li3Mg2NbO6 a = 8.552(2), b = 5.897(1), c = 17.721(5) Å; Li3Mg2SbO6 a = 8.614 (1), b = 5.908(1), c = 17.759(5) Å.
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    Applied crystallography online 15 (1982), S. 590-593 
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    Notes: The structure of the transition phase M′ in AlZnMg alloys has been studied by Buerger X-ray precession photographs and transmission electron microscopy. The M′ phase, also called η′ or R, has a hexagonal or pseudo-hexagonal cell with a = 4.96, c = 14.03 Å. It is confirmed that M′ precipitates are hexagonal platelets with the following epitaxy: (00.1)M′//(111)Al and |10.0|M′//1{\bar 1}0|Al. It is shown that none of the known models of the unit cell accounts for the observed scattered intensities.
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    Applied crystallography online 15 (1982), S. 602-604 
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    Notes: An improved `substitution method' for the separation of X-ray diffraction α1−α2 doublets is based on the possibility of refining both the proportionality constant between the α1 and α2 contributions to the line intensity and the doublet separation expressed in terms of the diffraction angle or of a related variable in the reciprocal space. Optimization of these two parameters, with a proper evaluation of the error, clearly shows the statistical nature of the oscillations appearing on the high-angle side of the pure α1 component after correction; their elimination by polynomial smoothing can therefore be performed and a procedure is suggested for achieving this result. A computer program, based on these principles, has been written and tested in many practical cases.
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    Applied crystallography online 15 (1982), S. 611-614 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The precipitation behavior in the Ti–27at.%Nb–6at.%Ta–6at.%Zr alloy aged at 643 K was examined by means of time-of-flight neutron small-angle scattering. When the alloy was aged, fine-scale α precipitates appeared. During the precipitation process, each precipitate grew in size, but the total number of precipitates remained nearly constant up to 1 Ms of ageing. The increase of critical superconducting current density could be connected with increasing size of α precipitates. The specimen for the measurements consisted of a composite containing 3721 filaments in a copper matrix. The use of neutrons was shown to give great advantages for the investigation of precipitation phenomena.
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  • 100
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 632-632 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The wrong original was used for Fig. 6(b) of Gastaldi, Jourdan, Marzo, Allasia & Jullien [J. Appl. Cryst. (1982), 15, 391–395]. The correct version of Fig. 6(b) is given. In Fig. 6(c) the growth time increases from right to left.
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