Simulations of the premelting of Al(110)

The premelting of Al(110) is studied by molecular dynamics simulations using the potential for Al derived from effective medium theory. We find a progressive disordering of the surface region as the bulk melting point is approached. This disorder is mediated by the formation of adatom–vacancy pairs. Based on the calculated radial distribution function and the analytical expression for the energy, it is demonstrated that the thermodynamics of disorder and melting is reflected in the single particle properties by a decrease in the number of nearest neighbors. The Debye temperature for the surface layer as determined from the simulations is θD ∼250 K, compared to θD ∼320 K found for the deeper layers. The thickness of the surface region determined from the Debye temperature is 3–4 layers. From an examination of the properties of some order parameters, we find that the premelting appears anisotropic only for some choices of order parameter. This has implications for the detection of the disorder by a diffraction technique.