Darstellung und Kristallstruktur der Hochdruckphase AgAlS2-II / Preparation and Crystal Structure of the High-pressure Phase AgAlS2-II

1974 ◽  
Vol 29 (3-4) ◽  
pp. 186-189 ◽  
Author(s):  
Klaus-Jürgen Range ◽  
Gerd Engert ◽  
Armin Weiss
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Coordination Number ◽  
High Pressure Phase ◽  
Chalcopyrite Structure ◽  
Space Group ◽  
Octahedral Sites ◽  
Tetrahedral Sites ◽  
Pressure Phase ◽  
Silver Atoms

AgAlS2-I with chalcopyrite structure transforms at 25 kbar and 300°C to the new highpressure phase AgAlS2-II. The crystal structure of AgAlS2-II is trigonal, space group P3ml, with a= 3,50 Å, c = 6,84 Å and Z = 1. The structure is based on a hexagonally close packed arrangement of sulfur atoms with aluminium atoms in octahedral sites and silver atoms in tetrahedral sites. The AgS4-tetrahedra are considerably distorted, giving a coordination number 3 + 1 for the silver atoms.

High-Pressure Synthesis and Crystal Structure of the New Orthorhombic Polymorph β-HgB4O7

2005 ◽  
Vol 60 (8) ◽  
pp. 815-820 ◽  
Author(s):  
Holger Emme ◽  
Matthias Weil ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Ambient Pressure ◽  
Normal Pressure ◽  
High Pressure Phase ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
High Pressure Synthesis ◽  
Pressure Synthesis ◽  
Pressure Phase

The new orthorhombic polymorph β-HgB4O7 has been synthesized under high-pressure and hightemperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 600 °C. β-HgB4O7 is isotypic to the known ambient pressure phases MB4O7 (M = Sr, Pb, Eu) and the high-pressure phase β-CaB4O7 crystallizing with two formula units in the space group Pmn21 with lattice parameters a = 1065.6(2), b = 438.10(9), and c = 418.72(8) pm. The relation of the crystal structure of the high-pressure phase β-HgB4O7 to the normal pressure phase α-HgB4O7 as well as the relation to the isotypic phases MB4O7 (M = Sr, Pb, Eu) and β-CaB4O7 are discussed.

High-pressure synthesis and crystal structure of the strontium tungstate Sr3W2O9

2018 ◽  
Vol 74 (2) ◽  
pp. 120-124 ◽  
Author(s):  
Daisuke Urushihara ◽  
Toru Asaka ◽  
Koichiro Fukuda ◽  
Hiroya Sakurai
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Pressure Phase ◽  
X Ray Diffraction ◽  
Rotation Symmetry ◽  
Synthesis And Crystal Structure ◽  
High Pressure Synthesis ◽  
Transmission Electron ◽  
Pressure Synthesis ◽  
Pressure Phase

The strontium tungstate compound Sr3W2O9 was prepared by a high-pressure synthesis technique. The crystal structure was determined by single-crystal X-ray diffraction and transmission electron microscopy. The structure was found to be a hettotype structure of the high-pressure phase of Ba3W2O9, which has corner-sharing octahedra with a trigonal symmetry. Sr3W2O9 has a monoclinic unit cell of C2/c symmetry. One characteristic of the structure is the breaking of the threefold rotation symmetry existing in the high-pressure phase of Ba3W2O9. The substitution of Sr at the Ba site results in a significant shortening of the interlayer distances of the [AO3] layers (A = Ba, Sr) and causes a distortion in the crystal structure. In Sr3W2O9, there is an off-centre displacement of W6+ ions in the WO6 octahedra. Such a displacement is also observed in the high-pressure phase of Ba3W2O9.

scholarly journals Persistence of the stereochemical activity of the Bi3+ lone electron pair in Bi2Ga4O9 up to 50 GPa and crystal structure of the high-pressure phase

2010 ◽  
Vol 66 (3) ◽  
pp. 323-337 ◽  
Author(s):  
Alexandra Friedrich ◽  
Erick A. Juarez-Arellano ◽  
Eiken Haussühl ◽  
Reinhard Boehler ◽  
Björn Winkler ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
High Pressure ◽  
Density Functional ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
High Pressure Phase ◽  
Functional Theory ◽  
Pressure Phase ◽  
Stereochemical Activity

The crystal structure of the high-pressure phase of bismuth gallium oxide, Bi2Ga4O9, was determined up to 30.5 (5) GPa from in situ single-crystal in-house and synchrotron X-ray diffraction. Structures were refined at ambient conditions and at pressures of 3.3 (2), 6.2 (3), 8.9 (1) and 14.9 (3) GPa for the low-pressure phase, and at 21.4 (5) and 30.5 (5) GPa for the high-pressure phase. The mode-Grüneisen parameters for the Raman modes of the low-pressure structure and the changes of the modes induced by the phase transition were obtained from Raman spectroscopic measurements. Complementary quantum-mechanical calculations based on density-functional theory were performed between 0 and 50 GPa. The phase transition is driven by a large spontaneous displacement of one O atom from a fully constrained position. The density-functional theory (DFT) model confirmed the persistence of the stereochemical activity of the lone electron pair up to at least 50 GPa in accordance with the crystal structure of the high-pressure phase. While the stereochemcial activity of the lone electron pair of Bi^{3+} is reduced at increasing pressure, a symmetrization of the bismuth coordination was not observed in this pressure range. This shows an unexpected stability of the localization of the lone electron pair and of its stereochemical activity at high pressure.

Crystal Structures of the High Pressure Phases ZnAs and CdAs

1976 ◽  
Vol 31 (2) ◽  
pp. 158-162 ◽  
Author(s):  
J. B. Clark ◽  
Klaus-Jügen Range
Keyword(s):  
High Pressure ◽  
Crystal Structures ◽  
Normal Pressure ◽  
High Pressure Phase ◽  
Diamond Structure ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Structural Relationships ◽  
Structure Relationship ◽  
Pressure Phase

The structure of the high pressure compounds ZnAs and CdAs have been determined using Guinier film and counter methods. The compounds are orthorhombic, (space group Pbca; Z = 8), with α = 5.679(2) Å, b = 7.277(4) Å, c = 7.559(4) Å and α = 5.993(4) Å, b = 7.819(6) Å, c = 8.011(6) Å respectively.ZnAs and CdAs are isostructural with the normal pressure phases ZnSb and CdSb, which are related to the high pressure phase Si III. Structural relationships are discussed including the Si III-diamond structure relationship.

Preparation and crystal structure of a new high-pressure phase (V0.5Re0.5)O2 with rutile-type structure

2003 ◽  
Vol 218 (7) ◽  
Author(s):  
K. G. Bramnik ◽  
H. Ehrenberg ◽  
R. Theissmann ◽  
H. Fuess ◽  
E. Morán
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Complex Oxide ◽  
High Pressure Phase ◽  
Type Structure ◽  
Pressure Phase

AbstractThe new complex oxide (V

Structural characterization of a new high-pressure phase of GaAsO4

2006 ◽  
Vol 62 (6) ◽  
pp. 1019-1024 ◽  
Author(s):  
David Santamaría-Pérez ◽  
Julien Haines ◽  
Ulises Amador ◽  
Emilio Morán ◽  
Angel Vegas
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Pressures ◽  
Ambient Conditions ◽  
Hexagonal Cell ◽  
Octahedral Sites ◽  
New Phase ◽  
Pressure Phase

As in SiO2 which, at high pressures, undergoes the α-quartz → stishovite transition, GaAsO4 transforms into a dirutile structure at 9 GPa and 1173 K. In 2002, a new GaAsO4 polymorph was found by quenching the compound from 6 GPa and 1273 K to ambient conditions. The powder diagram was indexed on the basis of a hexagonal cell (a = 8.2033, c = 4.3941 Å, V = 256.08 Å3), but the structure did not correspond to any known structure of other AXO4 compounds. We report here the ab initio crystal structure determination of this hexagonal polymorph from powder data. The new phase is isostructural to β-MnSb2O6 and it can be described as a lacunary derivative of NiAs with half the octahedral sites being vacant, but it also contains fragments of the rutile-like structure.

Crystal structure of a new superconducting high-pressure phase in the YBaCuO-System

1988 ◽  
Vol 73 (3) ◽  
pp. 313-319 ◽  
Author(s):  
C. Beli ◽  
H. -U. Nissen ◽  
Y. Kawamata ◽  
P. Stadelmann
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Pressure Phase ◽  
Pressure Phase

Crystal Structure of the High Pressure Phase of Bismuth Bi-III

2001 ◽  
Vol 378-381 ◽  
pp. 469-475 ◽  
Author(s):  
O. Degtyareva ◽  
M.I. McMahon ◽  
R.J. Nelmes
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Pressure Phase ◽  
Pressure Phase
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