Deformation of electron densities in static external fields: shape group analysis for small molecules

Abstract

The deformability of electron density provides important information regarding the reactivity and interaction of molecules. Part of this information is contained in directional parameters, such as the polarizability tensor. However, these electrostatic quantities do not provide sufficient insight regarding how the actual molecular shape is affected by the presence of an external electromagnetic field. We present an approach which describes quantitatively the local and global features of the deformation of electron densities by electric fields. The essential idea is to follow the change in the topological characterization of 3D electronic isodensity contours when the field is applied. For the sake of illustration, the present analysis is restricted to static uniform electric fields applied to diatomic and triatomic molecules. The results show how the description accounts for the nature of the molecule and the change in the orientation of the external field. It is possible as well to discriminate with accuracy how differently the regimes of low and high density values are affected by the perturbation.