Structure and metastability of superheated Al(111)

The high-temperature properties of the Al(111) surface are studied by molecular-dynamics simulation. This surface does not melt below the bulk melting point, but can be superheated. Superheating of metal surfaces has been observed recently in several experiments. A molecular-dynamics study of the structural properties reveals how after going through the superheating regime melting occurs over the whole crystal in a narrow temperature range. The temperature dependence of the surface stress, the mean-square vibrational amplitudes, and the anomalous outward expansion of the distance between two top layers an calculated. A transition from superheated to liquid state is analyzed using a kinetic description for the formation of liquid nuclei by the Fokker-Planck equation and conservation of heat at the liquid-solid interface.