High-pressure structural phase transitions in CuWO4

TL;DR

This study investigates how pressure induces structural, vibrational, and magnetic phase transitions in CuWO4 using experiments and calculations, revealing a transition at 10 GPa and effects of non-hydrostatic stresses.

Contribution

It provides combined experimental and theoretical evidence for pressure-induced phase transitions and magnetic changes in CuWO4, including new insights into the equation of state and stress effects.

Findings

Structural phase transition at 10 GPa from triclinic to monoclinic structure.

Second phase transition at 17 GPa under non-hydrostatic stress.

Determined the equation of state parameters for the triclinic phase.

Abstract

We study the effects of pressure on the structural, vibrational, and magnetic behavior of cuproscheelite. We performed powder x-ray diffraction and Raman spectroscopy experiments up to 27 GPa as well as ab initio total-energy and lattice-dynamics calculations. Experiments provide evidence that a structural phase transition takes place at 10 GPa from the low-pressure triclinic phase (P-1) to a monoclinic wolframite-type structure (P2/c). Calculations confirmed this finding and indicate that the phase transformation involves a change in the magnetic order. In addition, the equation of state for the triclinic phase is determined: V0 = 132.8(2) A3, B0 = 139 (6) GPa and = 4. Furthermore, experiments under different stress conditions show that non-hydrostatic stresses induce a second phase transition at 17 GPa and reduce the compressibility of CuWO4, B0 = 171(6) GPa. The pressure dependence of all Raman modes of the triclinic and high-pressure phases is also reported and discussed.