ABINITIO CALCULATIONS ON CL-(H2O)14 CLUSTERS - COMPARISON WITH THE RESULTS FROM MOLECULAR-DYNAMICS SIMULATIONS

Recently, Perera and Berkowitz have presented molecular dynamics simulations on Cl-(H2O)14 using two models, one additive (TIP4P) and the other nonadditive (POL1). Rather different structures emerged from then simulations, with the POL1 model predicting "Cl- outside" structures to be more favorable, and TIP4P predicting "Cl- inside to be more favorable. We have carried out ab initio quantum mechanical calculations at the STO-3G, STO-4G(d), 6-31G, 6-31G(d), and 6-31G(d)/MP2 levels on two low energy geometries resulting from each of the molecular dynamics models. At all levels of ab initio theory, the "Cl- outside' model created by POL1 is the lowest in energy with DELTAE0 of -166.4 and -223.7 kcal/mol at 6-31G(d) and 6-31G(d)/MP2. respectively, compared to the average potential energy of -151 kcal/mol found by Perera and Berkowitz.