Calibration of a computational scheme for solvation studies:: halide ions bound to water X(H2O)- (X = F, Cl, Br)

This study investigates the effect of basis set on the DFT-derived geometries and energies of halide ion-water complexes towards determining the optimum computational scheme for the study of larger clusters. It is shown that currently available methods are unable to adequately describe the anion-water clusters, mainly due to the residual BSSE even when the largest basis sets are used. This is also reflected in the fact that a basis-set converged geometry is not obtained even at the B3LYP/aug-cc-pV5Z level. There also appears to be a significant difference in geometry when counterpoise-corrected optimizations are performed at this level, suggesting that BSSE is the major contributor to the difficulties in modelling these systems.