Incomplete melting of the Au(100) surface

We study the high-temperature disordering of the reconstructed Au(100) surface by molecular-dynamics simulation using a many-body interatomic potential. We find that the surface deconstructs at 0.8Tₘ, where Tₘ is the bulk melting temperature, in good agreement with experimental data, but proper surface melting does not occur close to the bulk melting point. Instead, there is an in-plane disordering of the two topmost layers. The thickness of the disordered region remains constant with increasing temperature, indicating blocked, or incomplete, melting of the (100) crystalline substrate. An analysis of the structure reveals that crystalline and disordered islands coexist on the first two surface layers for temperatures between those for deconstruction and bulk melting.