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As one of the founders of quantum chemistry, Robert G. Parr (RGP) was an influential theoretical chemist of the last few decades. He made enormous scientific contributions to both wave function theory and density functional theory. He was also the founding father of conceptual density functional theory. RGP was both a devoted scientist and a family man. RGP met the love of his life, Jane Bolstad (who passed away on January 26, 2020, at the age of 97), at the University of Minnesota when they were graduate students. They successfully navigated 72 years of marriage with three children, Steven Parr of Tokyo, Jeanne Lemkau and Carol Lachenman, both of Chapel Hill. [ABSTRACT FROM AUTHOR]

The bonding and antibonding character of individual molecular orbitals has been previously shown to be related to their orbital energy derivatives with respect to nuclear coordinates, known as dynamical orbital forces. Albeit usually derived from Koopmans' theorem, in this work we show a more general derivation from conceptual DFT, which justifies application in a broader context. The consistency of the approach is validated numerically for valence orbitals in Kohn–Sham DFT. Then, we illustrate its usefulness by showcasing applications in aromatic and antiaromatic systems and in excited state chemistry. Overall, dynamical orbital forces can be used to interpret the results of routine ab initio calculations, be it wavefunction or density based, in terms of forces and occupations. [ABSTRACT FROM AUTHOR]

We discuss an extension of the venerable Parr‐Pearson parabolic charge transfer model that explicitly includes 3rd order effects. We then use this new model to provide new arguments supporting the validity of Parr and Yang's "|Δμ| big is good" (DMB) principle. Additionally, we show how to re‐derive this principle from the Parr‐Pearson parabolic model, using simpler arguments than those presented in our previous proof of the DMB rule. [ABSTRACT FROM AUTHOR]

We argue that when one divides a molecular property into atom‐in‐a‐molecule contributions, one should perform the division based on the property density of the quantity being partitioned. This is opposition to the normal approach, where the electron density is given a privileged role in defining the properties of atoms‐in‐a‐molecule. Because partitioning each molecular property based on its own property density is inconvenient, we design a reference‐free approach that does not (directly) refer atomic property densities. Specifically, we propose a stockholder partitioning method based on relative influence of a molecule's atomic nuclei on the electrons at a given point in space. The resulting method does not depend on an “arbitrary” choice of reference atoms and it has some favorable properties, including the fact that all of the electron density at an atomic nucleus is assigned to that nucleus and the fact all the atoms in a molecule decay at a uniform asymptotic rate. Unfortunately, the resulting model is not easily applied to spatially degenerate ground states. Furthermore, the practical realizations of this strategy that we tried here gave disappointing numerical results. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We analyze the Hamiltonian-interpolating schemes in chemical compound space. We show that if one allows for system-dependent information there are trivial solutions to this problem that allow to linearly interpolate between any two given iso-electronic Hamiltonians. If, on the other hand, one do not use any information about the system's Hamiltonians, we prove that there are no system-independent multiplicative interpolating procedures that linearize the energy. [ABSTRACT FROM AUTHOR]

The general-purpose reactivity indicator (GPRI) is utilized to discern the reactive sites of the phenylsulfinate ion, PhSO 2-, both in isolation and with a sodium counterion. While some approaches based on the hard/soft acid/base (HSAB) principle fail to indicate that the oxygens are the hard (electrostatic) sites of the molecule and that the sulfur is the soft (electron-transfer) site of phenylsufinate, the GPRI succeeds. A computer code, written in Fortran, that computes the general-purpose reactivity indicator is released in the supplementary information. [ABSTRACT FROM AUTHOR]

When a molecule is in the presence of a chemical reagent, the external potential and the number of electrons in the molecule change. This leads to perturbative perspectives on chemical reactivity, wherein the response of a molecule to various “model perturbations” of the external potential and number of electrons is used to predict its reactivity. The perturbative perspective allows one to treat indices associated with conceptual density functional theory in a unified way. Here we concentrate on the implications of the perturbative perspective in describing regioselectivity and certain global properties of molecules, specifically, their electrophilicity, nucleofugality, and electrofugality. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]