Local order and dynamic properties in liquid Au-Ge eutectic alloys by ab initio molecular dynamics

We report the results of first-principles molecular dynamics simulations for liquid and undercooled eutectic Au72Ge28 alloys at various temperatures. In comparison with the parent Au81Si19 liquid, we find a much less pronounced chemical short-range order in Au72Ge28, mainly due to the increasing influence of Ge-Ge nearest neighbor packing. In addition, a structural analysis using three-dimensional pair-analysis techniques evidences an icosahedral short-range order and its evolution with temperature, closer to that of pure Au than to that of Au81Si19. We use such differences to understand the dynamic properties of both systems and to discuss disparities in other properties of Au72Ge28 and Au81Si19 alloys.