Magnetic Gold: First-principles investigation of stable Au2+ in a mixed-valence halide perovskite*

Halide perovskites are attractive materials for solar energy conversion applications due to their strong light-matter interactions, structural tunability, and the relative ease with which they can be synthesized and processed. In this talk we present first-principles computational results on the perovskite Cs4AuIIAuIII2Cl12, an extended solid with putative Au2+ sites, which is stable under ambient conditions and was only recently synthesized for the first time. Using density functional theory, we compute the electronic structure and explain how its complex vacancy ordering leads to disproportionation into 2+ and 3+ Au sites. Alongside our computational results, we also rationalize the emergence of magnetism in this structure. Our data and theoretical arguments provide insights into the mechanism behind the novel oxidation state and emergent magnetic ordering. Additionally, this work further guides the design of next-generation halide perovskite-based functional materials.