EFFECT OF ELECTRON CORRELATION ON THE ELECTROSTATIC POTENTIAL DISTRIBUTION OF MOLECULES

A study on the effect of the electron correlation on the electrostatic potential distribution in molecules is presented. The study is focused not only on the features of the molecular electrostatic potential (MEP), but also on the atomic charges and dipoles. Electron correlation is introduced by means of the CIPSI and full-CI methods by using both 6-31G* and 6-31G basis sets. The results reported in this paper clearly point out the reliability of the CIPSI method to reproduce the features of the MEP evaluated from full-CI wave functions. Comparison of MEPs computed from SCF and full-CI wave functions indicates that the electron correlation does not have a uniform effect on the MEP in the whole space surrounding the molecule. Thus, electron correlation has a relevant effect near the nuclei, but the MEP determined from the SCF wave function remains largely unaffected in regions located outside the van der Waals sphere. Indeed, the characteristics of the SCF MEP minima undergo only a small change when electron correlation is considered.