Showing papers on "Electron backscatter diffraction published in 1977"
113 citations
TL;DR: X-ray diffraction experiments of a single crystal of magnetite at 84 K were carried out to investigate the crystal symmetry below the transition temperature as discussed by the authors, and a new lattice deformation which makes crystal symmetry lower than rhom-bolaedral was clarified.
Abstract: X-ray diffraction experiments of a single crystal of magnetite at 84 K were carried out to investigate the crystal symmetry below the transition temperature. A new lattice deformation which makes the crystal symmetry lower than rhom-bolaedral was clarified. The extra reflections which appear in the low temperature phase were observed for the first time with X-ray diffraction. The extinction of (4, 4, \(\pm\frac{1}{2}\)) reflections, which was found by Iizumi and Shirane by means of neutron diffraction, was also confirmed. All the experimental results can be explained reasonably by assuming that the low temperature phase of magnetite has monoclinic symmetry, and the space group is either C s 4 - C c or C 2 h 6 - C 2/ c .
77 citations
TL;DR: Some recent results of charge density analysis by X-ray and neutron diffraction are discussed in this paper, including the nature of single, double, and triple bonds, lone-pair hybridization, bonding in some metals, alloys, and organometallic compounds.
Abstract: Some recent results of charge density analysis by X-ray and neutron diffraction are discussed. Problems that have been studied in a number of laboratories include the nature of single, double, and triple bonds, lone-pair hybridization, bonding in some metals, alloys, and organometallic compounds, and the derivation of physical properties from X-ray diffraction densities. At the present stage of development of methods studies of series of related compounds are feasible and expected to find widespread application.
61 citations
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51 citations
01 Jan 1977
TL;DR: In this article, it is shown that surface defects of various kinds and various amounts are always present and it is therefore desirable to check which information on surface structure besides periodicity may be derived from diffraction experiments.
Abstract: Although single crystal surfaces frequently are assumed to be atomically flat and strictly periodic along the surface, in reality surface defects of various kinds and various amounts are always present. In nearly all surface physics laboratories, equipment for electron diffraction is available. It is therefore desirable to check which information on surface structure besides periodicity may be derived from diffraction experiments.
48 citations
47 citations
47 citations
TL;DR: The structure of NaTaO3 has been determined from X-ray powder diffraction spectra by measuring the intensities of the difference reflexions caused by the deviations from the ideal cubic perovskite structure as mentioned in this paper.
Abstract: The structure of NaTaO3 has been determined from X-ray powder diffraction spectra by measuring the intensities of the difference reflexions caused by the deviations from the ideal cubic perovskite structure. The structure is compared with that determined on the basis of single-crystal measurements.
45 citations
TL;DR: In this paper, the structures of sodium and potassium cyanide have been studied by neutron powder diffraction as a function of temperature between 6 and 300 K. The orientation of the CN ions in the lowest temperature phase has been established, and the mechanism of the order-disorder phase transitions has been elucidated by a careful study of a superlattice line intensity in KCN.
Abstract: The structures of sodium and potassium cyanide have been studied by neutron powder diffraction as a function of temperature between 6 and 300 K. The orientation of the CN ions in the lowest temperature phase has been established, and the mechanism of the order–disorder phase transitions has been elucidated by a careful study of a superlattice line intensity in KCN.
TL;DR: In this article, the hcp ϵ phase which is obtained by splat quenching of Fe-C and FeC-Si alloys has been studied by electron diffraction and Mossbauer spectroscopy.
TL;DR: In this paper, a simple procedure for the identification of enantiomorphous space groups by electron diffraction is presented, based on the ability to determine the sense of an asymmetry in a projection, which is a property of N-beam dynamic diffraction.
Abstract: A simple procedure is presented for the identification of enantiomorphous space groups by electron diffraction. This is based on the ability to determine the sense of an asymmetry in a projection, which is a property of N-beam dynamic diffraction. The steps in this procedure follow those of the X-ray procedure which depends upon anomalous dispersion instead of dynamic scattering. To illustrate and test the electron-diffraction procedure, a space-group determination was carried out on a sample of dextrorotatory α-quartz: space group P3221 was found, in agreement with the findings of de Vries [Nature, Lond. (1958), 181, 1193].
TL;DR: On the basis of an electron diffraction analysis, the following structural information was obtained on vapour phase toluene molecules: rg(CC) mean 1.399 ± 0.002 Å, rg(C-C) 1.117 ± 0.005 Å (rg), the methyl C-H bonds are at least 0.020 Å longer than the phenyl C-C bonds which are not longer than those in benzene as discussed by the authors.
Abstract: On the basis of an electron diffraction analysis, the following structural information was obtained on vapour phase toluene molecules: rg(CC)mean 1.399 ± 0.002 Å, rg(C-C) 1.511 ± 0.008 Å, the mean length of the C-H bonds is 1.117 ± 0.005 Å (rg). The methyl C-H bonds are at least 0.020 Å longer than the phenyl C-H bonds which are not longer than those in benzene
TL;DR: In this article, the super-period block spacing is found to contain block spacings of 6H, 15R, 4H and 21R polytypes in SiC structures.
Abstract: Extremely large-period polytypes in SiC have been investigated by single-crystal X-ray diffraction and direct lattice imaging by electron microscopy, which has been found to be a more suitable technique for studying structures of extremely large periodicities. Some crystals giving rise to a diffuse streaking along h0.l reciprocal lattice rows when studied by X-ray diffraction, showed the presence of extremely long- period polytypes when investigated by electron microscopy. The c periodicity of such SiC structures (having periodicities of more than 1000 A) has been determined by this technique and the super-period block spacing is found to contain block spacings of 6H, 15R, 4H and 21R polytypes.
TL;DR: In this paper, the electron diffraction analysis of microtwins and HCP platelets in an FCC matrix has been reexamined, where the diffraction spots from thin plates are strongly elongated and true spot positions are analyzed in exact low-order matrix orientations.
TL;DR: In this paper, the structure of high T c Nb 3 Ge films was analyzed using tunneling, x-ray diffraction and transmission electron diffraction, showing that large lattice expansions and depressions of T c are produced when exposed to hydrofluoric acid, presumably due to inclusion of hydrogen.
Abstract: In an attempt to understand the structure of high T c Nb 3 Ge films we have utilized tunneling, x-ray diffraction and transmission electron diffraction. Tunneling experiments indicate that such films have an appreciable highly disordered component. In x-ray diffraction, only two anomalous diffraction peaks are observed which are not sufficient to identify the unknown phase. The complex electron diffraction patterns are interpreted most easily as evidence for superlattice formation. Finally we show that large lattice expansions and depressions of T c are produced when Nb 3 Ge films are exposed to hydrofluoric acid, presumably due to inclusion of hydrogen.
TL;DR: Ohshima et al. as mentioned in this paper made a qualitative study by electron diffraction of the short-range-order diffuse scattering from disordered Au-Pd, α phase Au-Zn, and α phase Ag-Mg alloys.
Abstract: A qualitative study was made by electron diffraction of the short-range-order diffuse scattering from disordered Au-Pd, α phase Au-Zn, and α phase Ag-Mg alloys. Twofold and fourfold splittings of diffuse maxima are observed at 100, 110 and equivalent positions on the diffraction patterns with the incident beam parallel to [001], in the composition ranges from about 28 to 62 at.% Pd for Au-Pd, from about 7 to 24 at.% Zn for Au-Zn and from about 11 to 28 at.% Mg for Ag-Mg systems. The separation of the split diffuse maxima increases monotonically with Pd, Zn or Mg content. The results can be interpreted with the Fermi-surface-imaging concept proposed by Krivoglaz. The variation with composition of the Fermi wave vector parallel to the [110] directions is discussed with the nearly-free-electron and the rigid-band models. The latter model is also applied to the experimental results for disordered Cu-Pd and Cu-Pt alloys reported by the present authors [Ohshima & Watanabe (1973). Acta Cryst. A29, 520-526].
TL;DR: The first use of EDINP was reported in this paper, which allows the constrained refinement of molecules in a crystal structure with neutron diffraction powder data, allowing the choice of the correct minimum in the presence of a number of false minima.
Abstract: The first use of a new program, EDINP, is reported. This program allows the constrained refinement of molecules in a crystal structure with neutron diffraction powder data. The structures of p-C6F4Br2 and p-C6F4I2 are determined by packing considerations and then refined with EDINP. Refinement is stable and rapid, and the data are sufficiently accurate to allow the choice of the correct minimum in the presence of a number of false minima. A fuller report on EDINP is planned.
TL;DR: In this article, a model involving arrays of secondary dislocations which accommodate the departure of the observed misorientation between the two grains from that of a nearby coincident site lattice is discussed.
Abstract: Suitably defocused and exposed electron diffraction patterns from a high-angle grain boundary in a polyerystalline Cu—Si alloy contain rows of multiple diffraction spots along two different directions at a small angular separation. These occur in association with the main reflections from the grains. Geometrical analysis of the observed diffraction effects shows that they can be related to structure in the boundary. Furthermore, a correlation between diffraction patterns and bright-field electron micrographs enables fringe systems in the images of the boundary to be related to the boundary structure. The results are discussed in terms of a model involving arrays of secondary dislocations which accommodate the departure of the observed misorientation between the two grains from that of a nearby coincident site lattice.
TL;DR: The surface structures of 2H-NbSe2 and 2H -MoS2 have been accurately determined by low-energy electron diffraction (LEED) techniques as discussed by the authors.
Abstract: The surface structures of 2H-NbSe2 and 2H-MoS2 have been accurately determined by low-energy electron diffraction (LEED) techniques. The crystal polytype is found to be unchanged at the surface and the lattice dimensions are found also to be unchanged, except for a 5% contraction of the top interplanar separation of MoS2. We present LEED data for 1T-TaS2, a compound in which charge-density-waveinduced transitions have been observed. The data suggest that the surface structure of 1T-TaS2 is also nearly identical to the bulk structure.