Influence of atomic-scale structure on the transport, ordering, and thermodynamics of partially ordered Cu-In alloys

Abstract

We demonstrate the atomic-level structural properties of liquid Cu-In alloy as a function of In concentration using Square-Well (SW) model potential function under random phase approximation. It was found that the concentration-dependent structure factor S(k) and its Fourier transform, radial distribution function g(r) are in good agreement with the results obtained by the X-ray diffraction technique. Transport coefficients like diffusion coefficient and shear viscosity of liquid Cu-In alloys were estimated through computed structural functions and SW potential function. Interdiffusion coefficients in the melts were computed by solving the well-known Einstein's equation for Brownian particles with SW pair potential under linear trajectory principal. The composition-dependent shear viscosity is calculated using computed diffusion data in modified Stokes-Einstein (SE) relation. Specifically, we demonstrate a breakdown of SE relation at low In concentration in liquid Cu-In alloy. Using model calculations, we investigate the thermodynamic properties of alloy such as enthalpy of mixing, Gibbs free energy of mixing, and entropy of mixing. The concentration-concentration fluctuation at the zero momentum vector SCC(0)shows that there is a strong chemical bond between hetero-atoms in the Cu-rich region of liquid Cu-In alloys. It is worth mentioning here that the computed values of SCC(0), without using any adjusting or experimental parameter are in excellent agreement with experimental values measured by activity data.