Dipole oscillator strength distributions, sum rules, mean excitation energies, and isotropic van der Waals coefficients for benzene, pyridazine, pyrimidine, pyrazine, s-triazine, toluene, hexafluorobenzene, and nitrobenzene

TL;DR

This paper constructs dipole oscillator strength distributions for several aromatic molecules using experimental and theoretical data, enabling accurate predictions of sum rules, excitation energies, and van der Waals coefficients, with high accuracy for mixed interactions.

Contribution

It introduces a method combining experimental, theoretical, and additive models with sum rule constraints to accurately predict dipole properties and van der Waals coefficients for multiple molecules.

Findings

Predicted dipole sum rules $S(k)$ and mean excitation energies $I(k)$ for the molecules.

Achieved over 96\% accuracy in estimating $C_{6}$ coefficients for unlike interactions.

Found a popular combination rule for $C_{6}$ coefficients to be accurate within 1\\% for most cases.

Abstract

Experimental, theoretical, and additive-model photoabsorption cross-sections combined with constraints provided by the Kuhn-Reiche-Thomas sum rule and the high-energy behavior of the dipole-oscillator-strength density are used to construct dipole oscillator strength distributions for benzene, pyridazine (1,2-diazine), pyrimidine (1,3-diazine), pyrazine (1,4-diazine), $s$-triazine (1,3,5-triazine), toluene (methylbenzene), hexafluorobenzene, and nitrobenzene. The distributions are used to predict dipole sum rules $S(k)$ for $-6 \le k \le 2$, mean excitation energies $I(k)$ for $-2 \le k \le 2$, and isotropic van der Waals $C_{6}$ coefficients. A popular combination rule for estimating $C_{6}$ coefficients for unlike interactions from the $C_{6}$ coefficients of the like interactions is found to be accurate to better than 1\% for 606 of 628 cases (96.4\%) in the test set.