Crystal Structure of 4H BaRuO3: High Pressure Phase Prepared at Ambient Pressure

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.

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Crystal structure of 4H BaRuO3: high-pressure phase prepared at ambient pressure

Acta Crystallographica Section A Foundations of Crystallography ◽

10.1107/s0108767396087119 ◽

1996 ◽

Vol 52 (a1) ◽

pp. C310-C310

Author(s):

S.-T. Hong ◽

A. W. Sleight

Keyword(s):

Crystal Structure ◽

High Pressure ◽

Ambient Pressure ◽

High Pressure Phase ◽

Pressure Phase

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

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229617017879 ◽

2018 ◽

Vol 74 (2) ◽

pp. 120-124 ◽

Cited By ~ 2

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.

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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

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768110010104 ◽

2010 ◽

Vol 66 (3) ◽

pp. 323-337 ◽

Cited By ~ 20

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.

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LEAD-CHALCOGENIDES UNDER PRESSURE: AB-INITIO STUDY

International Journal of Modern Physics Conference Series ◽

10.1142/s201019451301074x ◽

2013 ◽

Vol 22 ◽

pp. 612-618 ◽

Cited By ~ 1

Author(s):

DINESH C. GUPTA ◽

IDRIS HAMID

Keyword(s):

Phase Transition ◽

High Pressure ◽

Ab Initio ◽

Band Gap ◽

Rock Salt ◽

High Pressures ◽

Ambient Pressure ◽

High Pressure Phase ◽

Lead Chalcogenides ◽

Pressure Phase

ab-initio calculations using fully relativistic pseudo-potential have been performed to investigate the high pressure phase transition, elastic and electronic properties of lead-chalcogenides including the less known lead polonium. The calculated ground state parameters, for the rock-salt structure show good agreement with the experimental data. The enthalpy calculations show that these materials undergo a first-order phase transition from rock-salt to CsCl structure at 19.4, 15.5, 11.5 and 7.3 GPa for PbS, PbSe, PbTe and PbPo, respectively. Present calculations successfully predicted the location of the band gap at L-point of Brillouin zone as well as the value of the band gap in every case at ambient pressure. It is observed that unlike other lead-chalcogenides, PbPo is semi-metal at ambient pressure. The pressure variation of the energy gap indicates that these materials metalized under high pressures. For this purpose, the electronic structure of these materials has also been computed in parent as well as in high pressure phase.

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