Chapter 6 - Electron Density Analysis and Electrostatic Potential

Abstract

This chapter attempts to create an understanding about the electronic structure of molecules by using the concepts of molecular orbitals (MOs), electron density and its distribution in a molecule, and molecular electrostatic potential (ESP) surfaces. Population analysis methods have been used to work out the electron charge density on each atom and in the region between the atoms which are then used for the analysis of bonding in molecules. Methods such as Mulliken analysis, Löwdin analysis, the natural population analysis, and methods based on electrostatic potential such as CHELPG, Merz–Kollman–Singh, and restrained ESP have been described. This is followed by a detailed account of the method of calculation of ESP and the use of the combined plot of the electron density and ESP isosurfaces for getting information about the reactive sites of a molecule and the intermolecular interactions. By the end of the chapter, methods for getting insight into the interactions and bonding in molecules by combined use of MO analysis, population analysis, electron density analysis, and energy analysis have been described with suitable examples.