Surface effects in vibrational and melting properties of Pb clusters

Abstract

We have studied the structural, dynamical and thermodynamical behaviour of Pb clusters in the N=147-2057 range, using a phenomenological many-body potential and molecular dynamics. Cuboctahedral structures, previously found to be particularly stable for this system, are used as starting configurations at low T. Calculated size-dependent melting temperatures appear to be reasonably accounted for by Pawlow's law, Tm(N)=Tm(∞)-AN-1/3. The behaviour of the mean square displacements and direct structural observations suggest that melting initiates at the surface, in agreement with recent experimental observations. High-frequency surface peaks in the vibrational spectrum disappear as T approaches Tm, in coincidence with the onset of surface diffusion. © 1993 Springer-Verlag.