MOLECULAR NETWORKS IN POSITION, MOMENTUM, AND PHASE-SPACE - A CASE-STUDY ON SIMPLE HYDROCARBONS

The notion of a molecular network as a system of local density maxima, connected by gradient paths, is extended from position space and the underlying charge density to momentum and phase space, and the momentu m density and Husimi distribution, respectively. Local maxima and grad ient paths are identified in a series of nine small hydrocarbonic mole cules, and the resulting ''molecular graphs'' are interpreted in terms of symmetry and topology. For the example of a symmetric SN2 reaction , it is shown that the topology of the Husimi function based graphs ca n be useful for the classification of chemical species and their chang e. In an appendix, a few relationships among elements of the gradient and the Hessian of the Husimi distribution are derived and briefly dis cussed.