Pressure-Induced Phase Transitions and Electronic Structure Evolution of Ba₄Au

Considering previous studies on the high-pressure phases and compressibility of Ba-Au alloys with stoichiometries Au₂Ba, AuBa, and Au₂Ba₃, the concentration of the alkaline-earth metal Ba increased, and a particle-swarm optimization algorithm was employed to conduct comprehensive structure searches for the Ba₄Au compound at 0, 10, 20, and 50 GPa. First-principles calculations were subsequently carried out to investigate its structural evolution and electronic properties under compression. Enthalpy-difference calculations indicate that the I4/mmm phase of Ba₄Au transforms to the Cmmm phase at approximately 0.4 GPa. As pressure increases above 5.7 GPa, the I4/m structure becomes energetically more favorable than Cmmm-Ba₄Au, indicating that the Cmmm phase transforms to the I4/m phase at 5.7 GPa. Both phase transitions are first-order and accompanied by discernible volume collapses. Additionally, a comparative analysis of the electronic properties of Ba₄Au was performed before and after the phase transitions. In this study, theoretical guidance is provided for the exploration of the high-pressure structural evolution of Ba₄Au, and critical insights are offered regarding the changes that occur in its physical and chemical properties under compression.