We also evaluated accuracy by comparing the gas-phase molecular dipole moments they yield with corresponding gas-phase QM dipole moments evaluated at the MP2/aug-cc-pVTZ level of theory on the molecules used to train BCC-dPol parameters (Figure ). It is generally believed that gas-phase partial charges derived from HF/6-31G* QM level of theory are over-polarized for the gas-phase and are therefore fortuitously suitable for use in the condensed phase. However, a fixed, over-polarized electrostatic model is not ideal for use to simulate properties that involve large changes in the electrostatic environment of a molecule, such as the transfer free energies of a molecule from vacuum to water. The RESP-dPol and AM1-BCC-dPol models include explicit polarizability and thus, like other polarizable models, should be able to account for such changes in the electrostatic environment. We therefore would like them to generate accurate, rather than overpolarized, gas-phase molecular dipole moments. The gas-phase permanent molecular dipole moments from our models were cal-culated as: