THEORETICAL-STUDY OF MICROSCOPIC SOLVATION OF LITHIUM IN WATER CLUSTERS - NEUTRAL AND CATIONIC LI(H2O)(N) (N = 1-6 AND 8)

The structure, stability, and electronic state of Li(H2O)(n) (n = 1-6 and 8) clusters have been investigated by an ab initio molecular orbit al method, including electron correlation, and compared with those of their cations. The interior structure where the Li atom is surrounded by four H2O molecules in the first shell and more in the second shell is found to be the most stable for both neutral and cationic n greater than or equal to 4 clusters. The size dependence of the vertical ioni zation potentials of Li(H2O)(n) is in good agreement with the recent e xperiment. It decreases successively until n = 4 and becomes nearly co nstant for n greater than or equal to 4 bring close to the bulk limit of vertical detachment energies of (H2O)(n)(-). The excess electron is separated from Li and distributed outside the first-shell cavity in n greater than or equal to 4 clusters. The electronic state of the clus ters changes from a one-center atomic state for n less than or equal t o 3 to a two-center ionic state for n greater than or equal to 4 with a gradual localization of the excess electron. Dangling hydrogens inte racting with the excess electron play a role as actuators of the surfa ce state.