Lowering of surface melting temperature in atomic clusters with a nearly closed shell structure

We investigate the interplay of particle number, N, and structural properties of selected clusters with N = 12 up to N= 562 by employing Gupta potentials parameterized for Aluminum and extensive Monte Carlo simulations. Our analysis focuses on closed shell structures with extra atoms. The latter can put the cluster under a significant stress and we argue that typically such a strained system exhibits a reduced energy barrier for (surface) diffusion of cluster atoms. Consequently, also its surface melting temperature, T-S, is reduced, so that T-S separates from and actually falls well below the bulk value. The proposed mechanism may be responsible for the suppression of the surface melting temperature observed in recent experiments.