Showing papers on "Electron backscatter diffraction published in 1969"
TL;DR: The interface between inorganic crystalline and organic amorphous matter in the skeletal element appears to be the first example reported in nature of a periodic mninimal suirface.
Abstract: X-ray diffraction studies confirm that, with few exceptions, each skeletal element of echtinoderms is a single crystal of magnesium-rich calcite and that a relation exists between the shape of the element and the crystallographic a- and c-axes. The exceptions incluide the teeth of echinoids, and the calcareous ring as well as the anal teeth of holothurians. The tubercles of an echinoid plate begin their growth as parts of the single crystal of the plate; under the mechanical action of the spines that are attached to them, they become partly polycrystalline, as shown by scanning electron microscopy and by x-ray powder diffraction. The interface between inorganic crystalline and organic amorphous matter in the skeletal element appears to be the first example reported in nature of a periodic mninimal suirface.
198 citations
TL;DR: In this article, the theory of the direct comparison X-ray method of phase analysis is extended to correct for preferred orientation effects and texture parameters are defined to assess the type and intensity of preferred orientation using data from diffractometer patterns.
Abstract: 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.
159 citations
TL;DR: The general features, terminology, and method of the dynamical theory of X-ray diffraction are discussed in this paper, stressing the analogy with the general theory of small oscillations of a mechanical system.
Abstract: The general features, terminology, and method of the dynamical theory of X-ray diffraction are discussed, stressing the analogy with the general theory of small oscillations of a mechanical system.
110 citations
90 citations
43 citations
41 citations
39 citations
34 citations
TL;DR: Determination of the unit cell of crystalline particles by optical diffraction analysis of electron micrographs may establish the identity and help in approximating the molecular weight of the substances contained in the crystal.
Abstract: Determination of the unit cell of crystalline particles by optical diffraction analysis of electron micrographs may establish the identity and help in approximating the molecular weight of the substances contained in the crystal. This technique may be particularly helpful when isolation and purification of the crystalline material cannot be accomplished.
29 citations
TL;DR: It was shown that conventional aldehyde fixatives introduced changes in the diffraction pattern of fixed nerve, apparently as a result of significant extraction of both polar and non-polar lipids.
TL;DR: In this article, the molecular structures of gaseous (GeH 3 ) 3 P and (SiH 3 Sb) have been determined by the sector-microphotometer method of electron diffraction.
TL;DR: In this article, electron microscopic observations of the first suboxide phase formed in the Vanadium-Oxygen system were given, and the twinned structure of this phase and the direct resolution of a long period superstructure were presented.
TL;DR: Three methods by which electron diffraction may be applied to problems in electron microscopy are discussed from a fundamental point of view, and experimental applications with biological specimens are demonstrated for each case.
TL;DR: In this paper, the properties of ordered alloys Au4X, where X stands for various transition elements and their mixtures, have been studied using electron, x-ray, and neutron diffraction.
Abstract: Micro‐, chemical and magnetic structures of ordered alloys Au4X, where X stands for various transition elements and their mixtures, have been studied using electron, x‐ray, and neutron diffraction. Specific heat and electrical resistivity measurements have been carried out for Au4Ti, Au4(Ti0.5Cr0.5)Au4V, Au4(V0.5Mn0.5)Au4Cr, Au4(Cr0.5Fe0.5), and Au4Mn. The magnetic form factors are given for Au4Cr and Au4Mn.
TL;DR: The iridescence of a number of beetles in the family Carabidae is shown to be produced by diffraction gratings, with mean angles of the first and second orders from the zero-order spectrum correspond to grating spacings that are in reasonable agreement with those seen with the stereoscan electron microscope.
TL;DR: In this article, a comparison of intensity values from detailed computer calculations with observed intensities from perfect crystals is reviewed for the cases of convergent beam diffraction patterns from MgO crystals of uniform thickness and of dark-field images of wedge-shaped crystals of silicon.
Abstract: In order to obtain accurate data on structure factors from electron diffraction data, it is necessary to take into account the inevitable n-beam dynamical diffraction effects. The comparison of intensity values from detailed computer calculations with observed intensities from perfect crystals is reviewed for the cases of convergent beam diffraction patterns from MgO crystals of uniform thickness and of dark-field images of wedge-shaped crystals of silicon. An analysis of the sources of error in each case suggests that it may be possible to derive structure factor values with an accuracy of better than one per cent. The method, recently proposed by Watanabe et al. [Acta Cryst. (1968). A24, 249] for deriving structure factors from the values of accelerating voltages for which some Kikuchi lines disappear, is reviewed and possible sources of error are examined.
TL;DR: In this paper, it is suggested that n-beam calculations should be made in order to avoid serious error in the refinement stages of a structure analysis, especially for materials containing heavy atoms.
Abstract: Calculations based on n-beam dynamical diffraction theory have shown that the intensities of rings and arcs in diffraction patterns from polycrystalline materials are strongly dependent on the experimental conditions. For arc patterns from BiOCl, calculations confirm a revised formula for the intensities from very thin crystals and indicate dependences on the distributions of orientation, thickness and bending of the crystals which are sufficient to account for the wide deviations of recent experimental results from the predictions of the primary extinction formula, based on the two-beam approximation. Inferences regarding the possible errors in electron diffraction analysis of crystal structures, especially for materials containing heavy atoms, are drawn from calculations relating to the intensities of arc patterns from AgTISe2. It is suggested that n-beam calculations should be made in order to avoid serious error in the refinement stages of a structure analysis.
TL;DR: In this paper, the X-ray diffraction patterns of polysiloxane (R2SiO)n.n. where R= n-propyl, has been characterized through high-resolution Xray diffract patterns of the polycrystalline material and selected-area electron-beam diffraction pattern of single crystals.
Abstract: The crystalline polysiloxane (—R2SiO—)n. where R= n-propyl, has been characterized through high-resolution X-ray diffraction patterns of the polycrystalline material and selected-area electron-beam diffraction patterns of single crystals. The smallest unit cell consistent with the diffraction data is tetragonal, with dimensions a = 9.52 • 0.01 and c = 9.40 ± 0.05 . The probable space group is P41 (or P43).
TL;DR: In this paper, a least-squares method of analyzing joint neutron and X-ray diffraction data from the same crystal is described. But the procedure is applied to hexamethylenetetramine, where it is shown that a more satisfactory refinement is obtained than by analysing each set of data independently.
Abstract: A least-squares method of analysing joint neutron and X-ray diffraction data from the same crystal is described. The procedure is applied to hexamethylenetetramine, where it is shown that a more satisfactory refinement is obtained than by analysing each set of data independently.
01 Jan 1969
TL;DR: In this article, the lattice parameters of an unknown mineral can be measured using a precision goniometer stage for electron microscopes to an accuracy of better than ± 0.2%, although for the least favourable case, in which an axis is lying close to the electron beam, this is reduced to ±0.5 %.
Abstract: Availability of precision goniometer stages for electron microscopes has greatly increased the power of selected-area electron diffraction as a technique for species identification. Lattice parameters of an unknown mineral can be measured, using such a device, to an accuracy that is generally better than ± 0.2%, although for the least favourable case, in which an axis is lying close to the electron beam, this is reduced to ± 0.5 %. In addition the space group of an unknown substance can be identified with a very low level of ambiguity.
TL;DR: In this article, two methods for the direct presentation and precise determination of surface relief of diffraction gratings are described, both of which utilize metallic replication techniques and a comparison of the results obtained is made with an interferometric measuring technique and the results are in agreement to within the errors of measurement.
Abstract: Two methods for the direct presentation and precise determination of surface relief of diffraction gratings are described, both of which utilize metallic replication techniques. A comparison of the results obtained is made with an interferometric measuring technique and the results are in agreement to within the errors of measurement. Surface irregularities of 2 nm have been measured from the electron micrographs of the surfaces of diffraction gratings, but the methods are applicable to any similar surface study.