Pressure-Enriched Chemistry of Pt: Prediction and Synthesis of Dense Sodium Platinides

Abstract

Transition-metal anions, such as platinum (Pt) anions, are rare, and their unusual valence states may induce unique crystal topologies and novel properties. Although Pt anions have been reported, a high negative valence state of Pt and the route to obtain it have not been systematically studied. Herein, we report that high pressure can enrich the chemistry of Pt and result in various platinides through a reaction with sodium (Na). Using first-principles calculations in combination with an evolutionary algorithm, we discover several Na-rich platinides with unprecedented stoichiometries (e.g., Na 2 Pt, Na 4 Pt, and Na 5 Pt) and find that they adopt similar Pt−Na polyhedrons, where Pt can gain more than one electron donated by Na atoms. With the increase of the Na content, the ionicity of Pt becomes stronger. Frontier orbitals of Na 4 Pt and Na 5 Pt are not only dominated by Pt 5d orbitals, but also by Pt 6p orbitals. Furthermore, the predicted Na 2 Pt (space group: P6/ mmm) and Na 4 Pt (space group: I4/m) are synthesized in a diamond anvil cell (DAC) and characterized by synchrotron X-ray diffraction at 4.5 GPa. The strong anisotropic properties of Na 2 Pt and the intriguing frontier orbitals of Na 4 Pt induced by Pt anions are further discussed.

Largely Asymmetric Binary Mesocrystals beyond Inorganic Crystals Formed in Linear ABC/ABC Blends

“…In fact, our assumption rule can also generate those binary crystal lattices, which have been realized in binary metallic alloys as shown in Figure c. FCC-AC 7 is formed by adding one C-sphere to the octahedral void of the FCC-AC 6 . FCC-AC 12 with two C-spheres on each face is formed, corresponding to UB 12 . , FCC-AC 12 transforms into FCC-AC 13 when each of its octahedral voids is filled by one C-sphere …”

“…FCC-AC 7 is formed by adding one C-sphere to the octahedral void of the FCC-AC 6 . 61 FCC-AC 12 with two C-spheres on each face is formed, corresponding to UB 12 . 62,63 FCC-AC 12 transforms into FCC-AC 13 when each of its octahedral voids is filled by one Csphere.…”

Forming Platinide Phases under Pressure in the Cs–Pt System

“…Pt can also form an anion at ambient pressure. For instance, Cs 2 Pt and (Cs 2 Pt) 4 ·CsH were synthesized and determined to contain platinide (Pt 2– ) anions. , More recently, a series of dense sodium platinides were predicted using DFT in combination with an evolutionary algorithm, which was then experimentally confirmed using diamond anvil cells and characterized by synchrotron X-ray diffraction at 4.5 GPa …”

“…24,25 More recently, a series of dense sodium platinides were predicted using DFT in combination with an evolutionary algorithm, which was then experimentally confirmed using diamond anvil cells and characterized by synchrotron X-ray diffraction at 4.5 GPa. 26 This work employs a particle swarm optimization (PSO) methodology to search for additional thermodynamically favorable phases containing an anionic platinum ion at ambient and high pressure. The Cs−Pt convex hull was first constructed using PSO methods and ab initio calculations to establish the most energetically favored crystal structures at various compositions and pressure.…”