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The eigenvectors of the electronic stress tensor can be used to identify where new bond paths form in a chemical reaction. In cases where the eigenvectors of the stress tensor are not available, the gradient-expansion-approximation suggests using the eigenvalues of the second derivative tensor of the electron density instead; this approximation can be made quantitatively accurate by scaling and shifting the second-derivative tensor, but it has a weaker physical basis and less predictive power for chemical reactivity than the stress tensor. These tools provide an extension of the quantum theory of atoms and molecules from the characterization of molecular electronic structure to the prediction of chemical reactivity. [ABSTRACT FROM AUTHOR]

Relationships between third-order reactivity indicators in the closed system [N, v(r)], open system [μ, v(r)], and density [ρ(r)] pictures are derived. Our method of derivation unifies and extends known results. Among the relationships is a link between the third-order response of the energy to changes in the density and the quadratic response of the density to changes in external potential. This provides a link between hyperpolarizability and the system’s sensitivity to changes in electron density. The dual descriptor is a unifying feature of many of the formulas we derive. [ABSTRACT FROM AUTHOR]

A justification for the likely presence of negative Fukui functions in molecules with small band gaps is given, and a computational study performed to check whether molecules with small band gaps have negative Fukui functions to a chemically significant extent is reported. While regions with negative Fukui functions were observed, significantly negative values for the atom-condensed Fukui functions were not observed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In our quest to explore molecules with chemically significant regions where the Fukui function is negative, we explored reactions where the frontier orbital that indicates the sites for electrophilic attack is not the highest occupied molecular orbital. The highest occupied molecular orbital (HOMO) controls the location of the regions where the Fukui function is negative, supporting the postulate that negative values of the Fukui function are associated with orbital relaxation effects and nodal surfaces of the frontier orbitals. Significant negative values for the condensed Fukui function, however, were not observed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The mechanism of a simple SN2 reaction, viz;OH–+ CH3F = CH3OH + F–has been studied within the framework of reactionforce and reactionelectronic flux. We have computationally investigated three differenttypes of reaction mechanisms with two different types of transitionstates, leading to two different products. The electronic transfercontribution of the reaction electronic flux was found to play a crucialrole in this reaction. Natural bond order analysis and dual descriptorprovide additional support for elucidating the mechanism of this reaction. [ABSTRACT FROM AUTHOR]

Abstract: We use the derivative of the electron density with respect to the reaction coordinate, interpreted through the Berlin binding function, to identify portions of the reaction path where chemical bonds are breaking and forming. The results agree with the conventional description for SN2 reactions, but they are much more general and can be used to elucidate other types of reactions also. Our analysis offers support for, and detailed information about, the use of the reaction force profile to separate the reaction coordinates into intervals, each with characteristic extents of geometry change and electronic rearrangement. [Copyright &y& Elsevier]

Abstract: The mechanism of charge-shift bonding is discussed from the perspective of the electronic stress tensor. In charge-shift bonds, the tensile mode of the stress tensor (attraction of electrons to the nuclei) is stronger, relative to the compressive modes (attraction of electrons toward the bond axis) than in conventional covalent bonds. Similar bonding indicators based on the eigenvalues of the tensor of second derivatives of the electron density and bond metallicity measures also correlate with charge-shift binding. These indicators seem preferable to the electron-density Laplacian and the local energy density because they can distinguish between weak covalent bonds and charge-shift bonds. [Copyright &y& Elsevier]