High pressure study of mixed valence compound CsAuI$_{3}$

CsAuI$_{3}$, chemically described as Cs$_{2}$Au$^{I}$Au$^{III}$I$_{6}$, is a mixed valence compound in the family of CsAuX$_{3}$ (X = Cl, Br, I), resembling the high Tc superconductor parent compound BaBiO$_{3}$. At ambient conditions it adopts a distorted perovskite structure with compressed Au$^{I}$X$_{6}$ octahedra and elongated Au$^{III}$X$_{6}$ octahedra along the crystallographic c-axis. The compound undergoes a pressure-induced transition into a new tetragonal phase comprising nearly equivalent AuX$_{6}$ octahedra around 5.3 GPa, which agrees with the valence transition previously reported using M\"{o}ssbauer spectroscopy between 8-12 GPa. We present a thorough high pressure studies of CsAuI3 through X-ray diffraction and Raman spectroscopy, confirming a pressure-induced band Jahn-Teller effect associated with the 5d$^{9}$ Au$^{II}$ ion. We will also report the reversible amorphization above 15 GPa.