Quantum-classical determination of stable isomers of the Li*Arn clusters

Abstract

We present a quantum-classical determination of stable isomers of LiArn, clusters with both an electronic ground state and excited states of the lithium atom. The Li atom is perturbed by argon atoms in LiArn clusters. Its electronic structure obtained as the eigenfunctions of a single-electron operator describing the electron in the field of a Li+Arn core, the Li+ and Ar atoms are replaced by pseudo-potentials. These pseudo-potentials include core-polarisation operators to account for the polarisation and correlation of the inert core with the valence lithium electron (Rhouma et al., 2002). The geometry optimisation of the ground and excited states of LiArn (n = 1–12) clusters is carried out via the Basin-Hopping method of Wales et al. (Wales and Doyle, 1997; Wales and Scheraga, 1999). The geometries of the ground and ionic states of LiArn clusters were used to determine the energy of the high excited states of the neutral LiArn clusters. The variation of the excited state energies of LiArn clusters as a function of the number of argon atoms shows an approximate Rydberg character, corresponding to the picture of an excited electron surrounding an ionic cluster core, is already reached for the 3s state.