THE IONICITY OF HALOGENS CHEMISORBED ON MERCURY REVISITED

The atop interaction of halogens (Cl, Br and I) above a finite surface cluster model has been studied at the ab initio Hartree-Fock level of theory employing non-empirical pseudopotentials and large basis sets. Two different electronic states have been considered corresponding formally to neutral and ionic interactions. The physical nature of the interaction emerging from the analysis of the resulting wavefunction can be different for each of these two electronic states. However, the use of a set of theoretical techniques, such as the study of the dipole moment curves or the effects induced by an external uniform electric field, allows us to show that in both cases the chemisorption bond between halogens and the surface model can be described as an ionic bond.