The structural, elastic, electronic and thermodynamic properties of hexagonal η-Cu6−xNixSn5 (x = 0, 0.5, 1, 1.5 and 2) intermetallic compounds

Based on first-principles calculations, the effects of various Ni concentrations on the structural, elastic, electronic and thermodynamic properties of hexagonal η-Cu6Sn5 compound have been systematically investigated. The results demonstrate that higher Ni concentration in the η-Cu6−xNixSn5 (x = 0, 0.5, 1, 1.5 and 2) leads to thermodynamically stable compounds, and Ni atoms preferentially occupy Cu2 + Cu1c sites forming the η-Cu4Ni2Sn5 compound. It is also found that the unit cell volume and lattice parameter of the 'a' axis decrease with increasing Ni concentration, which are consistent with the other experimental results. Furthermore, the polycrystalline elastic properties are obtained from single-crystal elastic constants. Our results indicate that the addition of Ni enhances the mechanical stability, brittleness, modulus and Debye temperatures of η-Cu6Sn5 compound. Analyzing the electronic structure and charge density distribution provides the explanation that Ni develops distinct bonding energy to Cu and Sn in the structure.