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.