Solute-solvent interaction energies for the benzene molecule dissolved in water are computed using Hartree-Fock and B3LYP density functional theories. Explicit solvent molecules up to 14-A away from the dissolved benzene molecule are included in the calculation of interaction energies. Both basis set dependence and basis set superposition errors are carefully examined. It is found that the use of a larger basis set for the region near the solute together with a smaller basis set for the outer region gives results very close to what would have been obtained if the larger basis set had been used for the whole system. It is also shown that a correction for the basis set superposition error is a necessary component in this kind of calculations. With this correction, results obtained with different tested basis sets converge to within 1 kcal/mol.
2008 Wiley Periodicals, Inc.