High-pressure structural behaviour of HoVO₄: combined XRD experiments andab initiocalculations

Abstract

We report a high-pressure experimental and theoretical investigation of the structural properties of zircon-type HoVO 4 . Angle-dispersive x-ray diffraction measurements were carried out under quasi-hydrostatic and partial non-hydrostatic conditions up to 28 and 23.7 GPa, respectively. In the first case, an irreversible phase transition is found at 8.2 GPa. In the second case, the onset of the transition is detected at 4.5 GPa, a second (reversible) transition is found at 20.4 GPa, and a partial decomposition of HoVO 4 was observed. The structures of the different phases have been assigned and their equations of state (EOS) determined. Experimental results have also been compared to theoretical calculations which fully agree with quasi-hydrostatic experiments. Theory also suggests the possibility of another phase transition at 32 GPa;i.e. beyond the pressure limit covered by present experiments. Furthermore, calculations show that deviatoric stresses could trigger the transition found at 20.4 GPa under nonhydrostatic conditions. The reliability of the present experimental and theoretical results is supported by the consistency between the values yielded for transition pressures and EOS parameters by the two methods.

High pressure phase transitions in NdVO4

“…Our lattice dynamics calculations suggest the possible occurrence of a new phase transition in NdVO 4 around this pressure. The post-monazite structure is proposed to have an orthorhombic structure as observed in related compounds 11,12 . However, the undoubtedly identification of the crystal structure of the new post-monazite phase is awaiting the confirmation of XRD experiments.…”

High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO4

“…However, as pressure increase and the Bi-O distances decrease, the strength of the bonds increases, due to electrostatic repulsions, making the Bi-O bonds as "hard" as the Sb-O bonds. This is a typical phenomenon of layered materials 51 GPa, 52 in vanadates below 10 GPa, 9 and in chromates even at lower pressures. 11 We think the large pressure stability of BiSbO 4 is caused by its layered structure, which thanks to the large compressibility of Bi-O bonds can accommodate the increasing repulsive and stearic stresses induced by pressure by deforming the irregular BiO 8 polyhedra, thereby avoiding the transformation to a high-pressure phase.…”

“…1,4,7,8 During the last decade, intensive investigations have been carried out on the structural evolution of MTO 4 -type ternary oxides under high-pressure (HP). They showed that compression is an efficient tool to improve the understanding of the main physical properties of vanadates, 9 phosphates, 10 chromates, 11 tungstates, 12 molydbates, 13 arsenates, 14 and many other MTO 4 compounds. 15 However, to the best our knowledge, an investigation of BiSbO 4 under pressure is still lacking in literature.…”

Cobalt ferrite nanoparticles under high pressure

“…This is a common phenomenon observed in many compounds. 30,31 Therefore, only data measured under quasi-hydrostatic conditions should be used to determine the bulk modulus from compression studies. In our case, if only the results measured under non-hydrostatic conditions are fitted with a second-order EOS, B 0 ¼ 284(25) GPa is obtained.…”