First-Principles and PSO-Driven Exploration of Ca-Pt Intermetallics: Stable Phases and Pressure-Driven Transitions

Abstract

In this study, first-principles calculations in conjunction with the particle swarm optimization (PSO) algorithm structure search method were employed to investigate the stable phases of Ca-Pt intermetallic compounds under various pressure conditions. The previously reported CaPt5 phase and the hitherto unreported phases Ca3Pt and Ca2Pt were successfully predicted, perfecting the known phase diagram for Ca-Pt intermetallic compounds. Furthermore, the pressure-induced phase transition in Ca2Pt has been identified. The structure of Ca2Pt undergoes a phase transition from Cmmm to C2/m and then to Cm at pressures ranging from 25 to 75 GPa. Electronic properties analyses revealed stable metallic bonds between the Ca and Pt atoms in the Ca-Pt intermetallic compounds. Simultaneously, the anionic character of the Pt atoms and the localization of electrons within the intermetallic compounds were observed. Analysis of the mechanical properties showed that Ca3Pt and CaPt5 exhibited different degrees of anisotropy. The CaPt5 structure exhibits significant transverse isotropy, whereas the Ca3Pt structure exhibits pronounced anisotropic behavior. The results of this study provide theoretical support for further research on Ca-Pt intermetallic compounds and the expansion of Pt oxidation states.

Keywords

• crystal structure prediction
• phase transition
• intermetallic compounds
• first-principles calculations