Entropy/information indices of the "stockholder" atoms-in-molecules

The information theory provides a solid foundation of Hirshfeld's "stockholder" partitioning of the molecular electron density into densities of bonded atoms. These entropy equilibrium, overlapping atoms-in-molecules constitute attractive concepts for the chemical interpretation of the molecular electronic structure. The local nature of this division scheme is emphasized in terms of the conditional probabilities of molecular subsystems. The Hirshfeld "information" channel for a given local volume element of constituent atoms, with the local promolecular ("input") and molecular ("output") conditional probabilities, is examined and its several local and global (molecularly averaged) conditional entropy and entropy deficiency descriptors are introduced and discussed. Illustrative numerical DFT (LDA) results for H-2 and HF are reported and the proposed entropy/information descriptors are examined as tools for diagnosing the chemical bonds. (C) 2004 Wiley Periodicals, Inc.