Inorganic structure types with revised space groups. I

Cenzual, K.; Gelato, Louise; Penzo, Marinella; Parthé, E.

doi:10.1107/s0108768191000903

Cited by 162 publications

(85 citation statements)

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“…2c, and Mn at (0, 1 2 , 0) and Bi at (0, 0.167(1), 1 4 ). This structure closely related to the structure adopted by Mn 1.08 Bi (space group P mma) [16], but without the excess Mn in the interstices. As discussed in the Supplemental Material, the Cmcm model is the simplest way to describe the distortion (it is a subgroup of the high temperature space group), and it fits the powder diffraction data well.…”

Section: A X-ray Diffractionmentioning

confidence: 86%

“…It has since been determined that near 630 K MnBi decomposes into Mn 1.08 Bi and Bi [15], both of which are paramagnetic at this temperature. The Mn rich phase is an orthorhombic variant of the NiAs-structure with the excess Mn occupying trigonal prismatic interstices similar to those occupied by the Bi atoms [16]. Since MnBi is ferromagnetic and the decomposition products are paramagnetic (at the peritectic temperature), application of strong magnetic field has been shown to stabilize MnBi to higher temperatures, up to about 650 K in a 10 Tesla magnetic field [17,18].…”

Section: Introductionmentioning

confidence: 99%

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Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

et al. 2014

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Structural and physical properties determined by measurements on large single crystals of the anisotropic ferromagnet MnBi are reported. The findings support the importance of magnetoelastic effects in this material. X-ray diffraction reveals a structural phase transition at the spin reorientation temperature TSR = 90 K. The distortion is driven by magneto-elastic coupling, and upon cooling transforms the structure from hexagonal to orthorhombic. Heat capacity measurements show a thermal anomaly at the crystallographic transition, which is suppressed rapidly by applied magnetic fields. Effects on the transport and anisotropic magnetic properties of the single crystals are also presented. Increasing anisotropy of the atomic displacement parameters for Bi with increasing temperature above TSR is revealed by neutron diffraction measurements. It is likely that this is directly related to the anisotropic thermal expansion in MnBi, which plays a key role in the spin reorientation and magnetocrystalline anisotropy. The identification of the true ground state crystal structure reported here may be important for future experimental and theoretical studies of this permanent magnet material, which have to date been performed and interpreted using only the high temperature structure.

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Section: A X-ray Diffractionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

et al. 2014

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“…The crystal structure of ε-GaSe is hexagonal, space group P6m2 ( 1 3h D , No. 187 [15,16]). In the Ref.…”

Section: Structural Detailsmentioning

confidence: 99%

Effect of pressure on the structural properties and electronic band structure of GaSe

Schwarz

Olguı́n

Cantarero

et al. 2006

Physica Status Solidi (b)

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The structural properties of GaSe have been investigated up to 38 GPa by monochromatic X-ray diffraction. The onset of the phase transition from the ε -GaSe to a disordered NaCl-type structural motif is observed near 21 GPa. Using the experimentally determined lattice parameters of the layered ε -phase as input, constrained ab-initio total energy calculations were performed in order to optimize the internal structural parameters at different pressures. The results obtained for the nearest-neighbor Ga -Se distance agree with those derived from recent EXAFS measurements. In addition, information is obtained on the changes of Ga -Ga and Se -Se bond lengths which were not accessible to a direct experimental determination yet. Based on the optimized structural parameters, we report calculations of band gap changes of ε -GaSe under pressure. The optical response and electronic band structure of the metallic high-pressure phase of GaSe are discussed briefly.

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“…See for example the succession of papers on the crystallographic description of Pb3Mn7015: Darriet, Devalette & Latourrette (1978), Marsh & Herbstein (1983), Le Page & Calvert (1984), Le Page (1987) and Holtstam, Lindqvist, Johnsson & Norrestam (1991 ). A number of wrong space-group assignments in descriptions of simple inorganic structure types, where all atoms were already in special positions with all coordinates fixed by the space-group symmetry, remained unnoticed for years until unquestionable additional symmetry was disclosed by Cenzual, Gelato, Penzo & Parth6 (1991) with use of the MISSYM program. Careful eye examination of structure plots followed by critical examination of symmetry elements suggested in MISSYM printouts, as detailed above, is currently the safest way known to us for deriving the space-group symmetry and thus reaching the conventional description of the structure under study Detailed comments are given below about the individual steps in the solution:…”

Section: Discussionmentioning

confidence: 99%

Derivation of conventional crystallographic descriptions of new phases from results of ab initio inorganic structure modelling

Page¹,

Klug²,

Tseb³

1996

J Appl Cryst

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The results of ab initio inorganic structure modelling are often in the form of Cartesian coordinates of atoms in a large, periodical and in general oblique simulation box containing hundreds to thousands of atoms. The contents of that box may correspond to a single crystal, a twin, a mixture of phases or a disordered block of matter. The problem of extracting corresponding crystallographic descriptions for single-crystal regions in the box, a necessary step in view of full quantum calculations and publication, is different from the familiar problem of extracting crystal symmetry and structure from experimental diffracted intensity data. The deductive computeraided method developed at the National Research Council of Canada over the years is based on eye identification of three pairs of atoms related by conjugate translations in the same single-crystal region on a stereo plot, followed by derivation of fractional coordinates for the atomic content of the corresponding primitive cell. Running this data through the MISSYM program discloses potential symmetry elements of the structure, with their corresponding crystallographic directions. These elements are then critically examined and accepted either as symmetry or pseudosyrnmetry on the basis of comparison of coordinate deviations between related atoms with the expected magnitude of thermal motion. All calculations described here can be performed with the NRCVAX system of programs.

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Inorganic structure types with revised space groups. I

Cited by 162 publications

References 0 publications

Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

Effect of pressure on the structural properties and electronic band structure of GaSe

Derivation of conventional crystallographic descriptions of new phases from results of ab initio inorganic structure modelling

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