Pressure is a fundamental thermodynamic variable that can dramatically influence the physical and chemical properties of materials. Applying pressure minimizes interatomic distances, modifies the electronic structure, chemical bonding, and alters the fundamental rules of chemistry. Pressure also enables the formation of new phases that may be inaccessible under ambient conditions by shifting the thermodynamic potentials. As a result, high pressure has emerged as an essential approach for creating compounds with atypical stoichiometries and unusual physical properties. Yet, despite expanded access to high-pressure synthesis techniques, these experiments remain complex and uncommon. The many challenges associated with high-pressure synthesis and crystal structure analysis have led to the development of computational-based crystal structure prediction algorithms to understand the complex crystal chemistry of inorganic solids at non-ambient pressure. In this study a series of platinide-containing phases were identified as thermodynamically favorable compounds at high pressure using an unbiased automatic crystal structure searching method. Density functional theory paired with a particle swarm optimization (PSO) algorithm supports that applying 10 GPa of pressure should result in three new phases: Cs2Pt, Cs2Pt3, and CsPt3. The transition metal is approximated to approach −1 due to charge transfer between Cs and Pt, as illustrated by Bader’s QM-AIM charge analysis and electron localization function (ELF) calculations. The identification of these phases also expands the known anionic 5d transition metals to include Ir, Pt and Au with the simplest compounds containing negatively charged gold achieved under ambient conditions, while compounds containing anionic platinum and iridium can be obtained with increasing pressure. These results support the presence of a series of rare pressure stabilized transition metal anions.

Pressure-stabilized anionic metals via particle swarm optimization

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ACS Fall 2022

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