First-principles study on structural, electronic, and superconducting properties of Laves-phase alloy HfZn ₂ under pressure

Abstract Laves-phase are among the most abundant groups of alloys with chemical formula AB 2 , 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 HfZn 2 , and discovered a phase transition from C 15 (space group <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>F</mml:mi> <mml:mi>d</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> ) phase to C 14 (space group P 6 3 / mmc ) phase at a pressure above 20 GPa. Based on ab initio simulations, the mechanical, chemical bonding and superconducting properties of high-pressure phase HfZn 2 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 C 14 phase of HfZn 2 under high pressure. Additionally, Zn gains approximately 0.43 electron from Hf at 10 GPa, and the superconducting critical temperature of HfZn 2 is estimated to be around 0.55 K at 50 GPa. Given that both C 14 and C 15 phases are common structures in Laves-phase alloys, elucidating the high-pressure behaviors of C 14 and C 15 phases of HfZn 2 will enhance the fundamental understanding of properties and potential applications at extreme conditions of Laves-phase alloys.