High-pressure x-ray diffraction study of SrMoO4 and pressure-induced structural changes

TL;DR

This study investigates the structural changes of SrMoO4 under high pressure using x-ray diffraction, revealing a reversible phase transition from a scheelite to a monoclinic fergusonite structure at 12.2 GPa.

Contribution

The paper provides the first detailed high-pressure x-ray diffraction analysis of SrMoO4, identifying a ferroelastic second-order phase transition and discussing its mechanism and anisotropic compressibility.

Findings

Phase transition at 12.2 GPa from scheelite to fergusonite structure.

No significant volume collapse during the transition.

Reversible structural modifications upon pressure release.

Abstract

SrMoO4 was studied under compression up to 25 GPa by angle-dispersive x-ray diffraction. A phase transition was observed from the scheelite-structured ambient phase to a monoclinic fergusonite phase at 12.2(9) GPa with cell parameters a = 5.265(9) A, b = 11.191(9) A, c = 5.195 (5) A, and beta = 90.9, Z = 4 at 13.1 GPa. There is no significant volume collapse at the phase transition. No additional phase transitions were observed and on release of pressure the initial phase is recovered, implying that the observed structural modifications are reversible. The reported transition appeared to be a ferroelastic second-order transformation producing a structure that is a monoclinic distortion of the low-pressure phase and was previously observed in compounds isostructural to SrMoO4. A possible mechanism for the transition is proposed and its character is discussed in terms of the present data and the Landau theory. Finally, the EOS is reported and the anisotropic compressibility of the studied crystal is discussed in terms of the compression of the Sr-O and Mo-O bonds.