The natural atomic orbital point charge model for PM3: Multipole moments and molecular electrostatic potentials

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Abstract
The natural atomic orbital/point (NAO‐PC) model originally developed to calculate molecular electrostatic potentials (MEPs) and multiple moments based on the AM1 wave function has been extended to PM3. As for AM1, NAO‐PC/PM3 reproduces dipole moments calculated by the standard PM3 method very well. There is also a surprisingly good correlation between experimental and calculated quadrupole moments. The MEPs calculated using PM3/NAO‐PC are found to be in better agreement with those given by RHF/6‐31G* than those obtained from the PM3 wave function using Coulson charges. On the other hand, the NAO‐PC model is often slightly worse then the method implemented in MOPAC‐ESP. The MEPs calculated using our model based on the PM3 wave function are often in better agreement with those given by RHF/6‐31G* than those obtain with AM1. © 1994 by John Wiley & Sons, Inc.