Journal of Chemical Physics, Vol.105, No.9, 3627-3635, 1996
Low-Momentum Electrons and the Electronic-Structure of Small Molecules
The electronic Husimi distribution eta((r) over right arrow,(p) over right arrow) is a "fuzzy" density in phase space. Sections through this function with a zero momentum variable ((p) over right arrow=0), are shown to be indicative of the spatial locations of chemical bonds and "free electron pairs" in molecules. The distribution eta((r) over right arrow;0) tends to focus on the inter-nuclear regions in position space. The Laplacian del(r)(2) eta((r) over right arrow;0), of the function may be used to enhance its diffuse features. The argument is made that the momentum-space Hessian of the Husimi function at the momentum-origin ((p) over right arrow=0), includes information about the "flexibility" of the electrons and the anisotropy of the latter. The diagonalization of this tensor supplies a pictorial map of preferred directions of electrons in the low-momentum, i.e., "valence" region of momentum space. Examples studied in this paper include the H-2, N-2, CH4, H2O, C2H4 and C6H6 systems in their Hartree-Fock approximation.