Microscopic solvation of anions in water clusters

Abstract We have studied the structure and energies of halide anion—water clusters X − (H 2 O) n , X = Cl, Br, I, and n =1−6 by ab initio molecular orbital calculations at the MP2 level. Information on energy-structure relationships emerged from the calculated ionization potentials, which are in good agreement with experiment for n = 1, 3, reveal the energetic stability of the surface anion state for n = 4,5 and indicate the transition from surface to interior anion states for n = 6.