Melting in small gold clusters: a density functional molecular dynamics study

Abstract

Molecular dynamics simulations of the thermal behaviour of gold clusters containing 7, 13and 20 atoms have been performed. Total energies and forces at each step of thesimulation are calculated from first principles using density functional theory. Iontrajectories are then calculated classically from these forces. In each case the globalminimum energy structure and a low-lying isomer are used as the starting structures.In most cases, the clusters do not exhibit a sharp transition from a solid-likephase to a liquid-like phase, but rather pass through a region of transformationsbetween structural isomers that extends over a considerable temperature range.Solid-like behaviour is observed in the atomic trajectories of the simulation attemperatures up to, or above, the bulk melting point. The 20-atom tetrahedralstructure is the one exception, showing a sharp transition between solid-like andliquid-like phases at about 1200 K. The starting structure used in the simulationis shown to have a considerable effect upon the subsequent thermal behaviour.