Wolframite-type MgReO4 under pressure: An experimental and theoretical study

Abstract

A combined high-pressure experimental and computational study of magnesium perrhenate, MgReO₄, is reported. Ambient-pressure X-ray diffraction confirms that MgReO₄ crystallizes in the wolframite-type structure, isostructural with MgWO₄. Synchrotron high-pressure X-ray diffraction measurements up to 20 GPa show that this structure is retained throughout the investigated pressure range. The compressibility of MgReO₄ is comparable to that of related wolframite-type oxides, including MgWO₄ and AWO₄ (A = Mn, Fe, Co, Ni, Zn, Cd). First-principles calculations reveal that the inclusion of spin-orbit coupling is essential for accurately reproducing the structural response under compression. Phonon calculations indicate dynamical stability over the entire pressure range. Electronic-structure calculations predict a metallic ground state at ambient pressure, and metallicity persists under compression within the studied pressure range, in marked contrast to the insulating behavior of most perrhenates. These results highlight the distinctive role of Re⁶⁺ chemistry and 5d electronic effects in determining the structural and electronic properties of technologically relevant ABO₄ oxides.