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.

scholarly journals The preparation and characterization of SeCl3SbF6, improved syntheses of MCl3(As/Sb)F6 (M = S, Se), and the X-ray crystal structure determination of SeCl3AsF6 and a new phase of SBr3SbF6

1996 ◽  
Vol 74 (9) ◽  
pp. 1671-1681 ◽  
Author(s):  
Jack Passmore ◽  
Paul D. Boyle ◽  
Gabriele Schatte ◽  
Todd Way ◽  
T. Stanley Cameron
Keyword(s):  
Crystal Structure ◽  
Raman Spectroscopy ◽  
Crystal Structures ◽  
Monoclinic Space Group ◽  
X Ray ◽  
Ft Raman Spectroscopy ◽  
New Phase ◽  
Ft Raman

Alternative and, in some cases, improved syntheses of the salts MX3(As/Sb)F6 (M = S, Se) and SCl3(SbCl6/AlCl4) are described. In addition, the synthesis of SeCl3SbF6 is reported. The compounds were characterized by FT–Raman spectroscopy and the X-ray crystal structures of SeCl3AsF6 (also 77Se NMR) and a new phase of SBr3SbF6 were determined. Crystals of SeCl3AsF6 and SBr3SbF6 are monoclinic, space group P21/c with [values for SBr3SbF6 in brackets] a = 7.678(1) [8.137(1)] Å, b = 9.380(3) [9.583(2)] Å, c = 11.920(3) [12.447(2)] Å, β = 98.19(2)° [97.36(1)]°, V = 849.72(3) [962.6(3)] Å3,z = 4, Dx = 2.925 [3.502] Mg m−3, R = 0.0525 [0.055], and Rw = 0.0554 [0.060] for 1151 [1472] observed reflections. Key words: MX3+ salts, FT–Raman spectroscopy, X-ray crystal structures of SeCl3AsF6, SBr3SbF6, and preparation of SeCl3SbF6.

Discovery of the High-Pressure Phase of Ba3W2O9 and Determination of Its Crystal Structure

2017 ◽  
Vol 56 (21) ◽  
pp. 13007-13013 ◽  
Author(s):  
Daisuke Urushihara ◽  
Toru Asaka ◽  
Koichiro Fukuda ◽  
Hiroya Sakurai
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Pressure Phase ◽  
Pressure Phase

β-CaB4O7: A New Polymorph Synthesized under High-Pressure/High-Temperature Conditions

2003 ◽  
Vol 58 (4) ◽  
pp. 257-265 ◽  
Author(s):  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Prominent Feature ◽  
X Ray ◽  
Temperature Conditions ◽  
High Pressure High Temperature ◽  
Ir Spectroscopic ◽  
Pressure Phase

A new oxoborate β -CaB4O7 has been synthesized under high-pressure/high-temperature conditions from calcium oxide and boron oxide with a Walker-type multianvil apparatus at 7.7 GPa and 1100 °C. Single crystal X-ray structure determination of β -CaB4O7 revealed: Pmn21, a = 1058.4(1), b = 436.9(1), c = 419.4(1) pm, Z = 2, R1 = 0.0305, wR2 = 0.0587 (all data). The compound is isotypic to the known oxoborates SrB4O7, PbB4O7, and EuB4O7 exhibiting a network structure of linked BO4 tetrahedra. As a prominent feature of the tetrahedral network an oxygen atom is coordinated to three boron atoms. The relation of the crystal structure of the high-pressure phase β -CaB4O7 to the normalpressure phase α-CaB4O7 as well as the relation to the isotypic phases MB4O7 (M = Sr, Pb, Eu) are discussed. The results of IR-spectroscopic investigations on β -CaB4O7 are also presented.

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.

Pressure-Induced Cationic Disordering in Pyrochlore Oxides (La1-xCex)2Zr2O7 and Enhancement of Compressibility

2014 ◽  
Vol 1033-1034 ◽  
pp. 583-587
Author(s):  
Fu Xiang Zhang ◽  
Maik Lang
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Pyrochlore Phase ◽  
Pyrochlore Structure ◽  
Fluorite Structure ◽  
High Pressure Phase ◽  
Ambient Conditions ◽  
Cation Site ◽  
Pyrochlore Oxides ◽  
Pressure Phase

Pyrochlore oxides La2Zr2O7,Ce2Zr2O7and their solid solutions were studied by in situ x-ray diffraction (XRD) measurement at high pressures. Pressure dependence of cationic disordering was derived from Rietveld refinement of the XRD patterns. The results indicated that the mixed occupancy in the cation site enhanced the compressibility obviously. All the pyrochlore structure became unstable at ~20 GPa and an orthorhombic high-pressure phase formed. The cations changed from the ordered state in pyrochlore to a disordered state in the high-pressure phase. The high-pressure phase is about 8% denser than the pyrochlore phase and not stable at ambient conditions and a disordered defect-fluorite structure was quenched for all the samples.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

scholarly journals New high-pressure phases of Fe7N3 and Fe7C3 stable at Earth's core conditions: evidences for carbon–nitrogen isomorphism in Fe-compounds

RSC Advances ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 3577-3581 ◽  
Author(s):  
Nursultan Sagatov ◽  
Pavel N. Gavryushkin ◽  
Talgat M. Inerbaev ◽  
Konstantin D. Litasov
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Ab Initio ◽  
Structure Prediction ◽  
Harmonic Approximation ◽  
Crystal Structure Prediction ◽  
Earth’S Core ◽  
Earth's Core ◽  
Core Conditions

We carried out ab initio calculations on the crystal structure prediction and determination of P–T diagrams within the quasi-harmonic approximation for Fe7N3 and Fe7C3.

scholarly journals Crystal and electronic structure engineering of tin monoxide by external pressure

2021 ◽  
Author(s):  
Kun Li ◽  
Junjie Wang ◽  
Vladislav A. Blatov ◽  
Yutong Gong ◽  
Naoto Umezawa ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Band Gap ◽  
High Pressures ◽  
Low Pressure ◽  
Widespread Application ◽  
Space Group ◽  
Tin Monoxide ◽  
High Possibility ◽  
Pressure Phase

AbstractAlthough tin monoxide (SnO) is an interesting compound due to its p-type conductivity, a widespread application of SnO has been limited by its narrow band gap of 0.7 eV. In this work, we theoretically investigate the structural and electronic properties of several SnO phases under high pressures through employing van der Waals (vdW) functionals. Our calculations reveal that a metastable SnO (β-SnO), which possesses space group P21/c and a wide band gap of 1.9 eV, is more stable than α-SnO at pressures higher than 80 GPa. Moreover, a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa. Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to β-SnO at around 120 GPa. Our work also reveals that β-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase α-SnO for the phase transition path Pnma-SnO →β-SnO → α-SnO. Two phase transition analyses indicate that there is a high possibility to synthesize β-SnO under high-pressure conditions and have it remain stable under normal pressure. Finally, our study reveals that the conductive property of β-SnO can be engineered in a low-pressure range (0–9 GPa) through a semiconductor-to-metal transition, while maintaining transparency in the visible light range.

Sign in / Sign up

Export Citation Format

Share Document