Novelp−Vrelationship in ReO3under pressure

Abstract

High-precision strain measurements on the metallic perovskite Re${\mathrm{O}}_3$ across the pressure-induced phase transformation at $p_{\mathrm{tr}}=5\mathrm{}$ kbar are reported. The crystals soften exponentially as the pressure approaches $p_{\mathrm{tr}}$ from below. The high-pressure phase exhibits large volume strain, proportional to ${(p-p_{\mathrm{tr}})}^{\frac{2}{3}}$ up to at least 30 kbar pressure. The abnormal $p-V$ relationship reflects either highly nonlinear restoring forces counteracting the rotations of the Re${\mathrm{O}}_6$ octahedra or the dominance of electron redistribution among subbands as in a Lifshitz transition.