TIGHT-BINDING CALCULATION OF SIZE DEPENDENCE OF THE IONIZATION-POTENTIALS OF MERCURY CLUSTERS

The gradual transition from van der Waals-like to metallic behaviour in mercury clusters is studied by localised orbital theory based on the tight-binding aproximation. The total density of states (DOS) of the Hg-n clusters is obtained by means of the moment expansion method. The Fermi energy determined from the DOS is combined with the classical conducting sphere droplet (CSD) model to calculate the size-dependent ionisation potential (IP) of the cluster. The theoretical results are in good agreement with the experiments. The size dependence of the ionisation potential has an abrupt change at n = 13, indicating that the transition from insulating to metallic behaviour begins.