LOW-MOMENTUM ELECTRONS AND THE ELECTRONIC-STRUCTURE OF SMALL MOLECULES

The electronic Husimi distribution eta((r) over right arrow,(p) over r ight arrow) is a ''fuzzy'' density in phase space. Sections through th is function with a zero momentum variable ((p) over right arrow=0), ar e shown to be indicative of the spatial locations of chemical bonds an d ''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 fu nction may be used to enhance its diffuse features. The argument is ma de that the momentum-space Hessian of the Husimi function at the momen tum-origin ((p) over right arrow=0), includes information about the '' flexibility'' of the electrons and the anisotropy of the latter. The d iagonalization of this tensor supplies a pictorial map of preferred di rections 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. ( C) 1996 American Institute of Physics.