SURFACE-INDUCED MELTING AND FREEZING .1. MEDIUM-ENERGY ION-SCATTERING INVESTIGATION OF THE MELTING OF PB(HKL) CRYSTAL FACES

Ion-shadowing and -blocking experiments on cylindrically shaped single crystals of Pb reveal a strongly orientation-dependent disordering (melting) of the surface as the temperature T increases toward the bulk melting point Tm. Most of the crystal faces become strongly disordered, but not the faces with orientations around the {111} and {100} planes. On the disordered surfaces the melted layer thickness is found to diverge logarithmically with increasing temperature. The disordering is shown to be driven by the orientation-dependent interface free energy which the ordered solid surface has in excess of a surface completely wetted with a liquid layer.