title: Structural characterization of a new high-pressure phase of GaAsO4.
abstract: As in SiO2 which, at high pressures, undergoes the alpha-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 A, V=256.08 A3), 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 beta-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.
authors.affiliation: Instituto de Química-Física Rocasolano, CSIC, C/Serrano 119, 28006 Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Santamaría-Pérez
authors.forename: Julien
authors.initials: J
authors.lastname: Haines
authors.forename: Ulises
authors.initials: U
authors.lastname: Amador
authors.forename: Emilio
authors.initials: E
authors.lastname: Morán
authors.forename: Angel
authors.initials: A
authors.lastname: Vegas
mesh_terms: D001149:Arsenates / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005708:Gallium / Q000737:chemistry*; D008958:Models, Molecular; D011312:Pressure; D012680:Sensitivity and Specificity
chemical_list: D001149:Arsenates; D005708:Gallium; C025657:arsenic acid