Formation and localization of a solvated electron in ground and low-lying excited states of Li(NH3)n and Li(H2O)nclusters: a comparison with Na(NH3)n and Na(H2O)n

Abstract

A theoretical study of the ground and low-lying excited states of Li(NH₃)_n and Li(H₂O)_n (n = 1–8) clusters is presented. Their structures, binding energies, vertical ionization energies and vertical transition energies were calculated using ab initio molecular orbital methods at correlated levels. Compared with Na(NH₃)_n and Na(H₂O)_n, the incremental binding energies and the spectroscopic energies are found to be almost metal-independent, but solvent-dependent after first-shell closure in both M(NH₃)_n and M(H₂O)_n (M = Li and Na) clusters_. Autoionization of the alkali atoms occurs via a spatial expansion of unpaired electron distribution extending to outside of the first solvation-shell, irrespective of the combinations of the metal and the solvent. The localization mode of the wave function of the solvated electron was investigated in both the ground and excited states. A change from a one-center diffuse state to a two-center localized state proceeds more quickly against n in M(H₂O)_n than in M(NH₃)_n, which is behind the solvent-dependence of the evaluated quantities.