Local order and dynamic properties of liquid and undercooled Cu55Hf45 and Cu62Hf38 alloys by ab initio molecular dynamics

Abstract

Atomic structures of liquid and undercooled Cu55Hf45 and Cu62Hf38 alloys have been studied using first-principles molecular dynamics simulations. It is found that both chemical short-range order and icosahedral short-range order are more pronounced at xCu = 0.55. We also evidence differences with the atomic structures of parent CuxZr1-x alloys. In examining the dynamic properties, we show that diffusivity and viscosity are closely related to the local structures of these two alloys. More particularly, we show that the icosahedral ordering is responsible for the more pronounced slowing down of the dynamics in the Cu55Hf45 alloy leading to a non-Arrhenius behavior in the undercooled region.