Two-step Liquid Drop Model for Binary, Metal-rich Clusters

It is shown that differences observed between the ionization potentials of the molecular-doped metallic clusters and those corresponding to the bare metallic ones can be explained by a two-step approach of the classical Liquid Drop Model. This approach takes into account the distinct physical properties of the interface between the molecular core and the metallic shell. Also, it is shown that the presence of the molecular core may act in the determination of the predominant channel of the coulombic fission. PACS : 36.40.-c ; 36.40.Wa ; 36.40.Qv Much of the recent interest in binary clusters has focused on the stability of atomic micro-objects consisting of metal atoms surrounding an electronegative impurity [1, 2, 3, 4, 5, 6, 7, 8]. There are mainly two interesting features exhibited in the behavior of the binary clusters. Most striking is the appearance of non-stoichiometric structures, i.e. the octet rule of the chemical bonding is apparently broken, in the size range of small clusters (a few metal atoms surrounding the electronegative element) [1, 2, 3, 4, 5, 6, 7]. Such systems are usually called hypervalent molecules. Nevertheless, by increasing progressively the number of metal atoms, the transition to metallicity appears as expected. It has been well demonstrated that the passage towards the metallic state is accompanied by a structural transition