First-Principles Study of Chemical and Topological Short-Range Orders in the Mg-Si Liquid Alloys

The structures of a series of Mg-Si liquid alloys were investigated by means of ab initio molecular dynamic simulation. The pair distribution function analysis manifests a tendency of aggregating for the Si-Si pairs in the Mg90Si10 liquid alloy. Chemical short-range orders are observed around Si atoms between unlike atoms, and the maximum is observed for the eutectic Mg47Si53 alloy. Furthermore, the topological environment changed abruptly near the eutectic Mg47Si53 alloy according to Voronoi polyhedra analysis. The variation of diffusion coefficients of Mg and Si suggests that the dynamical properties of Mg-Si liquid alloys are more sensitive to temperature than to compositions.