First–Principles Calculations of Cu Solid Solution Alloys by SQS Method

Abstract

We investigated structural and elastic properties of Cu–Ni and Cu–Zn solid solution alloys using first–principles calculations based on the special quasi–random structure （SQS） approach. The supercell modes composed of 108 atoms were employed. The atomic configurations of the supercell models was determined to set the Warren–Cowley parameter such that up to the seventh nearest–neighbor shell is close to zero. The formation energies in Cu–Ni and Cu–Zn alloys smoothly change with alloy composition, which indicates that the supercell models constructed based on the SQS method well reproduce the atomic arrangement of solid solution alloys. In Cu–Ni alloy, an overall increasing trend was observed with increasing Ni content for the Young’s and shear moduli. In the low concentration regions, local minima appeared due to the lattice strain around the solute atoms. In Cu–Zn alloy, the Young’s and shear moduli show sudden decreases at around 14 and 32 at％ Zn. In the composition at the local minima, the Fermi level lies at the sharp DOS peak, which leads to a suppression of energy loss by lattice strains. As a result, the Young’s and shear moduli are decreased. In Cu–Ni alloy, the fermi level lies near the 3d band and the change in the DOS around the fermi level is not significant in comparison with Cu–Zn alloy.