High-pressure Raman spectroscopy and lattice-dynamics calculations on scintillating MgWO4: A comparison with isomorphic compounds

TL;DR

This study combines high-pressure Raman spectroscopy and lattice-dynamics calculations to investigate structural phase transitions and vibrational properties of MgWO4 and related compounds, revealing a phase change at 26 GPa and comparing theoretical predictions with experimental data.

Contribution

It provides new insights into the high-pressure behavior of MgWO4, including phase transition details and the influence of non-hydrostatic conditions, along with a systematic comparison of theoretical calculations across related wolframites.

Findings

Phase transition at 26 GPa in MgWO4 under quasi-hydrostatic conditions.

Tentative assignment of high-pressure phase to triclinic structure similar to CuWO4.

Systematic discussion of theoretical calculation accuracy for multiple wolframite compounds.

Abstract

Raman scattering measurements and lattice-dynamics calculations have been performed on magnesium tungstate under high pressure up to 41 GPa. Experiments have been carried out under a selection of different pressure-media. The influence of non-hydrostaticity on the structural properties of MgWO4 and isomorphic compounds is examined. Under quasi-hydrostatic conditions a phase transition has been found at 26 GPa in MgWO4. The high-pressure phase has been tentatively assigned to a triclinic structure similar to that of CuWO4. We also report and discuss the Raman symmetries, frequencies, and pressure coefficients in the low- and high-pressure phases. In addition, the Raman frequencies for different wolframites are compared and the variation of the mode frequency with the reduced mass across the family is investigated. Finally, the accuracy of theoretical calculations is systematically discussed for MgWO4, MnWO4, FeWO4, CoWO4, NiWO4, ZnWO4, and CdWO4.