The fundamental principles of density functional theory are applied to achieve a better understanding various theoretical tools for describing chemical reactivity. Emphasis is given the Fukui function, central site reactivity index theory, which approached through its own variational principle. A maximum hardness principle then developed and discussed. To make contact with an earlier proof principle, changes in potential considered.

The computational approach to the Hirshfeld [Theor. Chim. Acta 44, 129 (1977)] atom in a molecule is critically investigated, and several difficulties are highlighted. It shown that these mitigated by an alternative, iterative version, of partitioning procedure. scheme ensures definition represents mathematically proper information entropy, allows be used for charged molecules, eliminates arbitrariness choice promolecule, increases magnitudes charges. resulting "Hirshfeld-I charges"...

Abstract When a molecule is in the presence of chemical reagent, external potential and number electrons change. This leads to perturbative perspectives on reactivity, wherein response various “model perturbations” used predict its reactivity. The perspective allows one treat indices associated with conceptual density functional theory unified way. Here we concentrate implications describing regioselectivity certain global properties molecules, specifically, their electrophilicity,...

For a linear combination of electron densities degenerate ground states, it is shown that the value any energy functional state energy, if exact for densities, size consistent, and translational invariant. The corresponding kinetic interaction functionals densities. Without invoking ensembles, fractional number electrons series straight lines interpolating its values at integers. These results underscore importance grand canonical ensemble formulation in density theory.

The derivation of the Hirshfeld atoms in molecules from information theory is clarified. importance for chemistry concept (AIM) stressed, and it argued that this concept, while highly useful, constitutes a noumenon sense Kant.

The dependence of molecular properties on the chemical hardness is explored. As a molecule increases, its size and polarizability typically decrease charge electronegativity increase. On basis these properties, interaction energy between hard soft acids bases quantified, physical global local hard/soft acid/base (HSAB) principles elucidated.

A comprehensive analysis is presented for the acid-base double-exchange reaction as well associated acid-displacement and base-displacement "half-reactions" with goal of elucidating meaning hard/soft acid/base (HSAB) principle conditions its validity. When electron-transfer effects are important other negligible, HSAB driven by surpassing stability soft acid/soft base product. electrostatic dominate reactivity, hard acid/hard Because favor soft/soft interactions, while hard/hard exchange...

We propose an approach to the electronic structure problem based on noninteracting electron pairs that has similar computational cost conventional methods electrons. In stark contrast other approaches, wave function is antisymmetric product of nonorthogonal geminals, but geminals are structured so projected Schrödinger equation can be solved very efficiently. focus where, in each geminal, only one orbitals a reference Slater determinant occupied. The resulting method gives good results for...

Atomic partial charges appear in the Coulomb term of many force-field models and can be derived from electronic structure calculations with a myriad atoms-in-molecules (AIM) methods. More advanced have also been proposed, using distributed nature electron cloud atomic multipoles. In this work, an electrostatic force field is defined through concise approximation density, for which interaction trivially evaluated. This approximate "pro-density" expanded minimal basis atom-centered s-type...

Abstract The Woodward‐Hoffmann rules for pericyclic reactions are explained entirely in terms of directly observable physical properties molecules (specifically changes electron density) without any recourse to model‐dependent concepts, such as orbitals and aromaticity. This results a fundamental explanation how the physics molecular interactions gives rise chemistry reactions. construction removes one key outstanding problems qualitative density‐functional theory chemical reactivity (the...

The second-order response of the electron density with respect to changes in number, known as dual descriptor, has been established a key reactivity indicator for reactions like pericyclic reactions, where reagents accept and donate electrons concurrently. Here we establish that descriptor is also ambiphilic reagents: can act either electrophiles or nucleophiles, depending on reaction partner. Specifically, study atoms (which are proposed act, simultaneously, an acceptor donor), molecules...

In a recent paper [J. Am. Chem. Soc. 2000, 122, 2010], the authors explored variational principles that help one understand chemical reactivity on basis of changes in electron density associated with reaction. Here, similar methods are used to explore effect changing external potential has reactivity. Four new indices defined: (1) energy surface results from second-order truncation Taylor series about some reference, Upsilon(R(1),R(2),.,R(M)()); (2) stabilization for equilibrium nuclear...

The hard/soft-acid/base (HSAB) principle indicates that hard acids prefer binding to bases (often forming bonds with substantial ionic character) while soft covalent character). Though the HSAB is a foundational concept of modern theory and bases, theoretical underpinnings remain murky. This paper examines exchange reaction, wherein two molecules, one product reacting acid base other base, substituents form preferred hard-hard soft-soft product. A simple derivation shows this reaction...

Two recent papers [P. W. Ayers and R. G. Parr, J. Am. Chem. Soc. 122, 2010 (2000); 123, 2007 (2001)] have shown how variational principles for the energy may be used to derive elucidate significance of chemical reactivity indices density-functional theory. Here, similar ideas are applied, yielding a systematic, mathematically rigorous, physically sound approach condensed indices. First, we use principle an expression Fukui function index in terms hardness kernel. Next, address important open...

Different procedures to obtain atom condensed Fukui functions are described. It is shown how the resulting values may differ depending on exact approach functions. The function can be computed using either fragment of molecular response or approach. two approaches nonequivalent; only latter corresponds in general with a population difference expression. Mulliken does not depend taken but has some computational drawbacks. different expressions tested for wide set molecules. In practice one...

In an attempt to master the overwhelming amount of data on properties substances and their reactions, chemists scrutinize them for underlying common patterns. modern times quantum mechanics (QM) has played a leading role in understanding chemical reactivity. late 1960s, Woodward Hoffmann (WH) proposed one most successful elegant approaches interpret outcome important type reaction: they could predict allowed or forbidden character pericyclic reactions through inspection phase symmetry...