Relationships between dissociation energies and electrostatic potentials of CNO2 bonds: applications to impact sensitivities

The dependence of net atomic charges, as derived from least-squares fitting to electrostatic potentials, on molecular orientation and potential site location is critically examined. A unique rotationally invariant algorithm, in which the charges may be constrained to reproduce the molecular dipole moment, is presented and the results for several basis sets compared to previous work. Significant improvements in dipole moments derived from the unconstrained charges are noted.

Derivation of net atomic charges from molecular electrostatic potentials

The molecular structure of 1-azanapthalene-8-ol was calculated by the B3LYP density functional model with 6-31G(d,p) basis set by Gaussian program. The results from natural bond orbital analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule. The stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital analysis. The electron density based local reactivity descriptors such as the Fukui functions were calculated. The dipole moment (μ) and polarizability (α), anisotropy polarizability (∆α) and rst order hyperpolarizability (βtot) of the molecule have been reported.

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Natural Bond Orbital (NBO) Population Analysis of 1-Azanapthalene-8-ol

A Monte Carlo quantum mechanical and molecular mechanical (QM/MM) simulation method using the combined Austin model 1 (AM1) and TIP3P potential is proposed to evaluate the average molecular electrostatic potentials (MEP) in aqueous solution. It was demonstrated that the average MEP in water can provide a quantitative account of the solvent polarization effect on molecular dipole moments and atomic charges. The computed induced dipole moments from the Monte Carlo AM1/TIP3P simulation method were found to be in good agreement with those predicted by continuum self‐consistent reaction field theory using the AM1 and 6‐31G(d) wave functions. The findings also indicate that the minimal basis set adopted by the AM1 method can capture the solvent effect effectively. Finally, good correlations in the MEP‐fitted charges were obtained between different methods. These results should be useful for developing polarizable intermolecular potential functions (PIPF).

Induced dipole moment and atomic charges based on average electrostatic potentials in aqueous solution

The charge‐dependent ‘‘effective’’ electronegativity χα of an atom α in a molecule or crystal, i.e., χα=(χ0α+Δχα)+2(η0α +Δηα)qα +∑β≠α qβ/Rαβ differs from the expression for the isolated atom (χ0α+2η0αqα) because of corrections to the electronegativity (Δχα) and hardness (Δηα), respectively, and due to the external potential generated by the surrounding charges qβ at distances Rαβ (new quantum‐mechanical proof given). After calibration of Δχα and Δηα for all atom types, ab initio charges can be reproduced to within a few hundredths of an electron by the electronegativity equilization method (using χav=χα=χβ⋅⋅⋅ and ∑β qβ=constant). Application of this algorithm to the solid state (i.e., charges and external potential being generated in a self‐consistent way and using Ewald’s method for determining the Madelung potential) leads to a novel method for determining ‘‘ab initio quality’’ charges and the value of the average electronegativity. If applied to SiO2 polymorphs, a relation between the refractive index ...

A.E. Foti

Papers

Charge distributions and chemical effects: Part XV. SCF—Xα—SW studies of alkanes