First Principles Study of Stability and Thermal Properties of AuxCuy Compounds

The stability and the thermal as well as mechanical properties of AuxCuy intermetallic compounds were investigated by density functional theory (DFT). The calculated cohesive energy and the formation enthalpy of AuxCuy phases show that they are thermodynamically stable structures and the calculated lattice constants are in good agreement with those of the experiments. The heat capacities of the compounds were calculated by a quasi-harmonic approximation (QHA) method. The Debyes temperature as a function of strength of chemical binding for each compound was also discussed. The elastic properties such as bulk modulus and Young's modulus were evaluated by Viogt-Reuss-Hill approximation. The phonon spectrum and the density of phonon states of AuCu compounds were calculated to determine the stability of two AuCu phases. The new knowledge from this study will be used for future development of Au-Cu alloy system.