Mechanical, electronic and thermal properties of Cu5Zr and Cu5Hf by first-principles calculations

Abstract

The structural, elastic, electronic and thermodynamic properties of Cu5Zr and Cu5Hf compounds are investigated by first-principles calculations combined with the quasi-harmonic Debye model. The calculated lattice parameters of cubic AuBe5-type Cu5Zr and Cu5Hf agree well with available experimental and other theoretical results and the formation enthalpy calculations show that AuBe5-type Cu5Hf is more energetically stable than the competing hexagonal CaCu5-type phase. The mechanical properties such as mechanical stabilities, anisotropy character, ductility (estimated from the value of B/G, Poisson’s ratio υ and Cauchy pressures C12–C44) and thermodynamic properties such as volume change under temperature and pressure (V/V0), heat capacity (Cv), Debye temperature (Θ), thermal expansion coefficient (α) of AuBe5-type Cu5Zr and Cu5Hf are calculated together. Cu5Hf has better performances than Cu5Zr with higher hardness and better resistance to fracture which are rationalized from the calculated electronic structure (including density of states, charge density distributions, Mulliken’s population analysis) and we find that all ionic, covalent and metallic components exist in bonding of Cu5Zr and Cu5Hf but the covalent bonding in Cu5Hf is stronger.