Cluster Simulations: Melting and Sintering

Abstract

A natural question about clusters concerns their phase changes. In particular, one may ask questions on the occurrence of surface melting and of what happens when two or more clusters with mobile surface layers are in contact. This is precisely a microscopic version of sintering. This chapter discusses the construction of efficient, approximate potentials from accurate ab initio potentials, the simulation of melting, surface melting, diffusion along grain boundaries, and derivation of the key transport parameters. It discusses simulation of homogeneous clusters, such as ArN and CuN and binary clusters exemplified by (KC1)N . The homogeneous clusters illustrate several points: first, how to construct approximate potentials for doing molecular dynamics from accurately computed potentials; second, how surfaces melt on small clusters; and third, how the sintering of two clusters appears in a classical simulation by molecular dynamics. The work on homogeneous clusters is seen as groundwork for studying metal clusters, their phase changes, and their sintering. The work on binary clusters is seen as the counterpart groundwork for studying ionic solids and ceramics. The work with salt clusters has, thus, far been oriented toward understanding the way these clusters, particularly small clusters with N of order 4 or 5, behave as more and more energy is put into them.