Quantum Entanglement and Chemical Reactivity.

The water molecule and a hydrogenic abstraction reaction are used to explore in detail some quantum entanglement features of chemical interest. We illustrate that the energetic and quantum-information approaches are necessary for a full understanding of both the geometry of the quantum probability density of molecular systems and the evolution of a chemical reaction. The energy and entanglement hypersurfaces and contour maps of these two models show different phenomena. The energy ones reveal the well-known stable geometry of the models, whereas the entanglement ones grasp the chemical capability to transform from one state system to a new one. In the water molecule the chemical reactivity is witnessed through quantum entanglement as a local minimum indicating the bond cleavage in the dissociation process of the molecule. Finally, quantum entanglement is also useful as a chemical reactivity descriptor by detecting the transition state along the intrinsic reaction path in the hypersurface of the hydrogenic abstraction reaction corresponding to a maximally entangled state.

Jensen-Tsallis divergence and atomic dissimilarity for position and momentum space electron densities.

Quantifying the dissimilarity among two or more many-electron systems by means of their one-particle densities is a hot topic within the physical applications of the information theory. This is a relevant achievement of the so-called "divergence measures," for which several definitions have been considered, each one with its own advantages and difficulties. Nevertheless, all of them are considered in order to disclose the differences among the involved systems, neutral atoms in the present work, according to their densities in the position and momentum spaces. The pioneering Jensen-Shannon divergence (JSD) constitutes a particular case of the one-parameter Jensen-Tsallis divergence (JTD). The analysis here provided for the JTD of atomic systems generalizes and improves some previous results on the JSD one. Such an improvement mainly arises from the capability of JTD to modify, by means of its characteristic parameter, the relative contribution of relevant specific regions of the atomic densities in both conjugated spaces.