In a recent paper [J. Chem. Phys. 105, 6471 (1996)], nonlinear chemical responses of a system to a simultaneous change of its external potential and of its number of electrons have been formulated in terms of the ground-state electronic density for a given model of the Hohenberg-Kohn functional. In the present work, an exact one-electron formulation of all the chemical responses is derived in terms of the Kohn-Sham orbitals of the unperturbed system. The present formulation encompasses the band-structure formulation of the linear Fukui function derived recently [M.H. Cohen, M.V. Ganduglia-Pirovano, and J. Kudrnovský, J. Chem. Phys. 101, 8988 (1994)] and provides an exact orbital expression of the linear hardness. The latter is compared to the hardness matrix used in the construction of ab initio pseudo-potentials [M. Teter, Phys. Rev. B 48, 5031 (1993)]. In addition, the relation between the covalent radius of atoms and the linear and nonlinear hardnesses is discussed.

Kohn-Sham orbital formulation of the chemical electronic responses, including the hardness

An extensive conventional ab initio and density functional theory investigation reveals that HXeI is a polar molecule with large multipole moments and highly anisotropic (hyper)polarizability. At the CCSD(T) level of theory our best values for the mean (hyper)polarizability are α¯∕e2a02Eh−1=101.46, β¯∕e3a03Eh−2=−850.7, and γ¯∕e4a04Eh−3=18.7×103. The corresponding anisotropies are Δα∕e2a02Eh−1=119.66, Δβ∕e3a03Eh−2=−2518.7, Δ1γ∕e4a04Eh−3=−249.1×103, and Δ2γ∕e4a04Eh−3=−99.6×103. The longitudinal components of the (hyper)polarizability are dominant. Our value for the anisotropy of the dipole polarizability is considerably larger than the recent empirical estimate of 22.9e2a02Eh−1 [N. H. Nahler et al., J. Chem. Phys. 119, 224 (2003)]. The results of the insertion of Xe into HI are quantified by the calculation of the differential (hyper)polarizability at the MP2 level of theory: α¯diff≡α¯(HXeI)−α(HI)−α¯(Xe)=36.29e2a02Eh−1 and γ¯diff≡γ¯(HXeI)−γ¯(HI)−γ¯(Xe)=18.1×103e4a04Eh−3.

How large is the static electric (hyper)polarizability anisotropy in HXeI

Many useful concepts developed within density functional theory provide much insight for the
understanding and prediction of chemical reactivity, one of the main aims in the field of conceptual
density functional theory. While approximate evaluations of such concepts exist, the analytical and
efficient evaluation is, however, challenging, because such concepts are usually expressed in terms of
functional derivatives with respect to the electron density, or partial derivatives with respect to the
number of electrons, complicating the connection to the computational variables of the Kohn-Sham
one-electron orbitals. Only recently, the analytical expressions for the chemical potential, one of the key
concepts, have been derived by Cohen, Mori-Sanchez, and Yang, based on the potential functional
theory formalism. In the present work, we obtain the analytical expressions for the real-space linear
response function using the coupled perturbed Kohn-Sham and generalized Kohn-Sham equations,
and the Fukui functions using the previous analytical expressions for chemical potentials of Cohen,
Mori-Sanchez, and Yang. The analytical expressions are exact within the given exchange-correlation
functional. They are applicable to all commonly used approximate functionals, such as local density
approximation (LDA), generalized gradient approximation (GGA), and hybrid functionals. The analytical
expressions obtained here for Fukui function and linear response functions, along with that for the
chemical potential by Cohen, Mori-Sanchez, and Yang, provide the rigorous and efficient evaluation of
the key quantities in conceptual density functional theory within the computational framework of the
Kohn-Sham and generalized Kohn-Sham approaches. Furthermore, the obtained analytical
expressions for Fukui functions, in conjunction with the linearity condition of the ground state energy as
a function of the fractional charges, also lead to new local conditions on the exact functionals,
expressed in terms of the second-order functional derivatives. We implemented the expressions and
demonstrate the efficacy with some atomic and molecular calculations, highlighting the importance of
relaxation effects

/pdf/analytical-evaluation-of-fukui-functions-and-real-space-ewcv5w2ire.pdf

Analytical evaluation of Fukui functions and real-space linear response function.

The antioxidant activity of molecules constitutes an important factor for the regulation of redox homeostasis and reduction of the oxidative stress. Cells affected by oxidative stress can undergo genetic alteration, causing structural changes and promoting the onset of chronic diseases, such as cancer. We have performed an in silico study to evaluate the antioxidant potential of two molecules of the zinc database: ZINC08706191 (Z91) and ZINC08992920 (Z20). Molecular docking, quantum chemical calculations (HF/6-31G**) and Pearson’s correlation have been performed. Molecular docking results of Z91 and Z20 showed both the lower binding affinity (BA) and inhibition constant (Ki) values for the receptor-ligand interactions in the three tested enzymes (cytochrome P450—CP450, myeloperoxidase—MP and NADPH oxidase—NO) than the control molecules (5-fluorouracil—FLU, melatonin—MEL and dextromethorphan—DEX, for each receptor respectively). Molecular descriptors were correlated with Ki and strong correlations were observed for the CP450, MP and NO receptors. These and other results attest the significant antioxidant ability of Z91 and Z20, that may be indicated for further analyses in relation to the control of oxidative stress and as possible antioxidant agents to be used in the pharmaceutical industry.

An In Silico Study of the Antioxidant Ability for Two Caffeine Analogs Using Molecular Docking and Quantum Chemical Methods

Applying Conventional Ab Initio and Density Functional Theory Approaches to Electric Property Calculations. Quantitative Aspects and Perspectives

This work rigorously relates electromagnetic properties and characteristics of molecular potential energy surfaces to the empirical concept of ‘‘softness,’’ used to categorize Lewis acids and bases, and to summarize observed patterns of reactivity. New equations are derived that connect infrared absorption intensities, vibrational force constants, intermolecular forces at first order, and linear electric‐field shielding tensors to softness kernels as defined in density functional theory. A generalization to nonlinear response—by introduction of the hypersoftness—leads to new equations in density‐functional terms for vibrational Raman band intensities, the cubic anharmonicities in molecular potential energy surfaces, intermolecular forces at second order, and nonlinear electric‐field shielding tensors. The analysis employs relations of the softness and hypersoftness to nonlocal polarizability and hyperpolarizability densities that represent the intramolecular distribution of response to inhomogeneous electric fields.

K. L. C. Hunt

Papers

Molecular softness, hypersoftness, infrared absorption, and vibrational raman scattering: new relations derived from nonlocal polarizability densities