A COMPREHENSIVE APPROACH TO MOLECULAR CHARGE-DENSITY MODELS - FROM DISTRIBUTED MULTIPOLES TO FITTED ATOMIC CHARGES

Some alternative methodologies for the construction of reliable charge density models, involving distributed multipole schemes, potential fi tted atomic charges, and a recent approach proposed by Ferenczy, are c ompared and analyzed critically. Ferenczy's method, which combines the distributed multipole description and the classical least-squares fit , allows one to get an insight into well-known shortcomings of standar d potential- or field-derived atomic charge models. It is now demonstr ated that the conformational dependence of fitted point charges is not exclusively due to through-space inductive effects, but that it can b e partly rationalized by the reorientation of the atomic multipoles. ( C) 1994 John Wiley & Sons, Inc.