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

Spreading of a molten Cu droplet on a cold Cu substrate is studied by molec ular dynamics simulations. An embebbed atom method (EAM) potential is used for both molten Cu droplet and Cu substrate. At the start, the molten dropl et equilibrated at 1500 K is placed on the surface of the substrate of 10 K . The spreading spontaneously occurs under the attractive atomic forces bet ween the molten droplet and substrate atoms. The snapshots of the spreading and solidification processes as well as the dynamic spreading behavior des cribed by a dimensionless spreading index are quite analogous to those obse rved 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 ca n persist via downward motion of the unsolidified atoms to the outside neig hbor positions of the frozen contact line which suggests that a no-slip bou ndary condition may apply to the spreading of a molten droplet on a cold su bstrate because of simultaneous rapid solidification. (C) 1999 Elsevier Sci ence B.V. All rights reserved.