Electron correlation effects on the topography of molecular electrostatic potentials

The effect of the inclusion of electron correlation at the MP2 level on the MESP topography is investigated. The change is analyzed in terms of the MESP value as well as eigenvalues at the critical point (CP). The pi-bond and lone-pair minima become more shallow and flat, and all the CPs indicating electron localization (negative MESP value) move outward due to the correlation correction. The volumes enclosed within the isopotential surface around a CP indicate the contraction of the MESP distribution due to electron correlation. The inclusion of the singles contribution in the MP2 density matrix is seen to be crucial to the MESP distribution. Both the positive as well as negative valued MESP regions become modified due to electron correlation.