Effect of the third element on the structure of liquid Mg65Cu25Y10 alloy

•Cu plays crucial role in Mg65Cu25Y10's chemical and topological SROs.•Additive elements decrease varieties and prolong lifetimes of Voronoi polyhedra.•Additive elements hinder the diffusion of Mg and Y efficiently.

The liquid structures of Mg65Cu25Y10 and its three homologous binary liquid alloys are investigated via ab initio molecular dynamics in the present work. The chemical and topological environments in all four liquid alloys are analyzed using pair distribution function, coordination number, and the Voronoi polyhedron. It shows that the Cu atoms play significant role in deciding the chemical and topological short-range orders of the Mg65Cu25Y10 liquid alloy. The Voronoi polyhedra in the ternary liquid alloy illustrate less varieties and longer lifetime. Moreover, the diffusion coefficients are decreased significantly in the ternary liquid alloys according to the mean square displacements. All above offer a deeper insight into how the three species work in the Mg65Cu25Y10 liquid alloy.