First-principles study on structural, electronic, and superconducting properties of Laves-phase alloy HfZn₂ under pressure

Laves-phase are among the most abundant groups of alloys with chemical formula AB₂, known for their high-temperature strength and potential application in hydrogen storage. The Laves-phase generally acts as a strengthening agent, which enhances the strength and durability of alloys at extreme conditions. Consequently, the properties of Laves-phase alloys at extreme conditions attract wide attention. In this study, we investigated the high-pressure phase diagram of Laves-phase alloy HfZn₂, and discovered a phase transition from C15 (space group $Fd\overline{3}m$) phase to C14 (space group P6₃/mmc) phase at a pressure above 20 GPa. Based on ab initio simulations, the mechanical, chemical bonding and superconducting properties of high-pressure phase HfZn₂ were predicted. The ratio of bulk modulus to shear modulus (B/G), a key indicator of mechanical properties in alloys, increases from 1.86 to 4.09 within the pressure range of 50–250 GPa, indicating excellent ductility of the C14 phase of HfZn₂ under high pressure. Additionally, Zn gains approximately 0.43 electron from Hf at 10 GPa, and the superconducting critical temperature of HfZn₂ is estimated to be around 0.55 K at 50 GPa. Given that both C14 and C15 phases are common structures in Laves-phase alloys, elucidating the high-pressure behaviors of C14 and C15 phases of HfZn₂ will enhance the fundamental understanding of properties and potential applications at extreme conditions of Laves-phase alloys.