Electronic and mechanical properties of η-Cu6Sn5 doped by Ni: A first-principles study

In this paper, based on the crystallographic characteristics of η-Cu6Sn5, a 1×1×5 supercell was constructed, and Ni atom was doped into each of the eight Cu2 sites respectively. The electrical and mechanical properties of η-Cu6Sn5 doped with Ni atom at Cu2 site were calculated by first principles method. The single-crystal elastic constants and poly-crystalline elastic moduli were acquired by using Voigt-Reuss-Hill approximations. The elastic anisotropies of the doping systems were characterized by a three-dimensional (3D) surface constructions and two-dimensional (2D) plane projections. The results show that the doping of Ni can reduce the elastic anisotropy of η-Cu6Sn5. The most significant decrease in elastic anisotropy is observed when Ni is doped at the Ni-1 position in η-Cu6Sn5. The doping of Ni can also alter the fracture toughness of η-Cu6Sn5. Adding Ni to some Cu2 sites can increase the shear resistance of η-Cu6Sn5. Through electronic structure calculations, it is found that the doping of Ni alters the electronic structure and stability of η-Cu6Sn5. Specifically, Ni-d orbitals hybridize with Sn-p orbitals, which in turn increases the peak value near −1.54 eV. When Ni is doped at the Ni-3 position, the stability of η-Cu6Sn5 increases the most; conversely, when Ni is doped at the Ni-1 position, the stability of η-Cu6Sn5 decreases the most.