Accurate Molecular Polarizabilities Based on Continuum Electrostatics

Abstract

A novel approach for representing the intramolecular polarizability as a continuum dielectric is introduced to account for molecular electronic polarization. It is shown, using a finite-difference solution to the Poisson equation, that the Electronic Polarization from Internal Continuum (EPIC) model yields accurate gas-phase molecular polarizability tensors for a test set of 98 challenging molecules composed of heteroaromatics, alkanes and diatomics. The electronic polarization originates from a high intramolecular dielectric that produces polarizabilities consistent with B3LYP/aug-cc-pVTZ and experimental values when surrounded by vacuum dielectric. In contrast to other approaches to model electronic polarization, this simple model avoids the polarizability catastrophe and accurately calculates molecular anisotropy with the use of very few fitted parameters and without resorting to auxiliary sites or anisotropic atomic centers. On average, the unsigned error in the average polarizability and anisotropy compared to B3LYP are 2% and 5%, respectively. The correlation between the polarizability components from B3LYP and this approach lead to a R2 of 0.990 and a slope of 0.999. Even the F2 anisotropy, shown to be a difficult case for existing polarizability models, can be reproduced within 2% error. In addition to providing new parameters for a rapid method directly applicable to the calculation of polarizabilities, this work extends the widely used Poisson equation to areas where accurate molecular polarizabilities matter.

Numerical Study on the Partitioning of the Molecular Polarizability into Fluctuating Charge and Induced Atomic Dipole Contributions

“…After diagonalizing the static molecular polarizability tensor (computed via finite differences), the anisotropy of the polarizability can be measured by 119 $$\Delta \alpha =\frac{\sqrt{\frac{1}{2}[{({\tilde{\alpha }}_{\mathrm{italicxx}}-{\tilde{\alpha }}_{\mathrm{italicyy}})}^2+{({\tilde{\alpha }}_{\mathrm{italicyy}}-{\tilde{\alpha }}_{\mathrm{italiczz}})}^2+{({\tilde{\alpha }}_{\mathrm{italiczz}}-{\tilde{\alpha }}_{\mathrm{italicxx}})}^2]}}{\frac{1}{3}({\tilde{\alpha }}_{\mathrm{italicxx}}+{\tilde{\alpha }}_{\mathrm{italicyy}}+{\tilde{\alpha }}_{\mathrm{italiczz}})},$$ where ${\tilde{\alpha }}_{\mathrm{italicxx}},{\tilde{\alpha }}_{\mathrm{italicyy}}$ and ${\tilde{\alpha }}_{\mathrm{italiczz}}$ are the real part of the three components of the diagonalized polarizability tensor $\tilde{\alpha }$. The results calculated at the B3LYP/6-31G(d) level of theory are depicted in Fig.…”

Polarization effects in molecular mechanical force fields

“…One parameter of this method includes a solute’s dielectric constant. Tan et al assumed that a universal dielectric constant of 4 is optimal for all molecules tested; however, Truchon et al (2008) found that this value may depend on the class of molecules.…”

“…Truchon et al (2008) employed the continuum dielectric to develop a new approach for computing gas-phase molecular polarizabilities based on a finite-difference solution to the Poisson equation. A molecule is treated as an entity with a high dielectric, which produces electronic polarization.…”

A finite field method for calculating molecular polarizability tensors for arbitrary multipole rank

“…Some common polarization models are based on induced dipoles 35–37 , Drude oscillators 38 , fluctuating charges 39–42 , and continuum dielectric models 43,44 . In many cases, the polarizability parameters are fit to or tested against experimental or theoretical molecular dipole-dipole polarizability tensors.…”