High-pressure structural behaviour of HoVO4: Combined XRD experiments and ab initio calculations

TL;DR

This study combines high-pressure XRD experiments and ab initio calculations to investigate the structural phase transitions of HoVO4, revealing irreversible and reversible transitions and the influence of stress conditions up to 28 GPa.

Contribution

It provides a comprehensive experimental and theoretical analysis of HoVO4's high-pressure phases, including transition pressures and structural assignments, with insights into stress effects.

Findings

Irreversible phase transition at 8.2 GPa under quasi-hydrostatic conditions

Reversible transition at 20.4 GPa under non-hydrostatic conditions

Theoretical prediction of a phase transition at 32 GPa

Abstract

We report a high-pressure experimental and theoretical investigation of the structural properties of zircon-type HoVO4. 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 HoVO4 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 non-hydrostatic 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.