Effective bond charges from infrared intensities: ab initio calculations

Abstract

Effective bond charges are calculated for a number of molecules from theoretically evaluated atomic polar tensors. The initial dipole moment derivatives are corrected for rotational and translational contributions and dependencies following a recently developed theoretical approach. Three levels of ab initio calculations are employed: HF/6-31G(d,p), HF/6-311+G(d,p) and MP2/6-31G(d,p). The effective bond charges obtained possess well-expressed relationships with molecular parameters that are determined from the electric charge distribution in molecules, such as the electronegativities of the constituent atoms, the bond ionicities and the hybridization state of the atoms. Such dependencies are most clearly expressed in structural analogs with identical symmetry.