Molecular dynamics of a molten Cu droplet spreading on a cold Cu substrate

Abstract

Spreading of a molten Cu droplet on a cold Cu substrate is studied by molecular dynamics simulations. An embebbed atom method (EAM) potential is used for both molten Cu droplet and Cu substrate. At the start, the molten droplet equilibrated at 1500 K is placed on the surface of the substrate of 10 K. The spreading spontaneously occurs under the attractive atomic forces between the molten droplet and substrate atoms. The snapshots of the spreading and solidification processes as well as the dynamic spreading behavior described by a dimensionless spreading index are quite analogous to those observed in recently reported experiments. A multiply twinned crystal structure is formed when the droplet is completely solidified. It is also shown that the contact line atoms are quickly solidified and trapped but spreading can persist via downward motion of the unsolidified atoms to the outside neighbor positions of the frozen contact line which suggests that a no-slip boundary condition may apply to the spreading of a molten droplet on a cold substrate because of simultaneous rapid solidification.