Atomistic characterization of solid-liquid interfaces in the Cu-Ni binary alloy system

Abstract

Molecular dynamics simulations based on an embedded-atom-method potential were performed to examine the structural and dynamical properties of the solid-liquid interfaces in the Cu-Ni alloy system with different orientations of the solid, i.e. (100), (110) and (111). The profiles of local order parameter, atomic number density, diffusion coefficients and Lindemann indices were evaluated and the interface widths were determined based on them. The widths are found to depend on the orientation of the underlying solid, while the orientation dependence for widths based on different criteria differs. The ones based on the local order parameter, given as the difference between an actual local atomic configuration and a referential ideal crystalline one, are found to be able to reflect the transitions across the interface in terms of both geometry and atomic motility, and are therefore most reliable. The interfacial layers are found to be composed of mixtures of both solid and liquid phases, the tempo-spatial variations of their relative amounts play an important role in determining the interfacial properties, including the interfacial widths. These findings can lend support to model the behavior of the solid-liquid interfaces at coarse grained scales, such as phase field modelling of dendrite growths.