Pressure-induced symmetry breaking in tetragonal CsAuI3

TL;DR

This study investigates how applying high pressure causes structural changes and amorphization in the mixed valence compound CsAuI3, revealing a reversible tetragonal to orthorhombic transition and potential valence state shifts.

Contribution

First in situ high pressure x-ray diffraction analysis of CsAuI3 revealing pressure-induced symmetry breaking and amorphization, with proposed structures for the high-pressure phase.

Findings

Reversible tetragonal to orthorhombic transition at 5.5-6 GPa

Reversible amorphization at 12-14 GPa

Discussion of possible gold valence transition mechanisms

Abstract

Results of in situ high pressure x-ray powder diffraction on the mixed valence compound Cs2Au(I)Au(III)I6 (CsAuI3) are reported, for pressures up to 21 GPa in a diamond anvil cell under hydrostatic conditions. We find a reversible pressure-induced tetragonal to orthorhombic structural transition at 5.5-6 GPa, and reversible amorphization at 12-14 GPa. Two alternative structures are proposed for the high-pressure orthorhombic phase, and are discussed in the context of a possible Au valence transition.