Accurate dipole moments from Hartree-Fock calculations by means of class IV charges

Charge Model 2 (CM2) is parameterized for Hartree-Fock calculations with the correlation-consistent polarized valence double zeta (cc-pVDZ) basis set. The resulting charge model has an RMS error of 0.18 D over a training set of 198 polar molecules. The charge model is additionally applied to 8 nucleic acid bases and methyl azide to test its performance for nitrogen-containing compounds not found in the training set. The results demonstrate that this new CM2 model based on ab initio Hartree-Fock calculations is robust in predicting the charge distributions of such molecules. Comparison of CM2 results for the nitrogen-containing test set with those from a previous charge model, charge model 1 (CM1) based on AM1 (Austin model 1) and PM3 (parameterized model 3) wave functions, indicate that the CM2 charges are more accurate than those from the previous model.