A discrete solvent reaction field model for calculating molecular linear response properties in solution

Abstract

A discrete solvent reaction field model for calculating frequency-dependent molecular linear response properties of molecules in solution is presented. The model combines a time-dependent density functional theory ͑QM͒ description of the solute molecule with a classical ͑MM͒ description of the discrete solvent molecules. The classical solvent molecules are represented using distributed atomic charges and polarizabilities. All the atomic parameters have been chosen so as to describe molecular gas phase properties of the solvent molecule, i.e., the atomic charges reproduce the molecular dipole moment and the atomic polarizabilities reproduce the molecular polarizability tensor using a modified dipole interaction model. The QM/MM interactions are introduced into the Kohn-Sham equations and all interactions are solved self-consistently, thereby allowing for the solute to be polarized by the solvent. Furthermore, the inclusion of polarizabilities in the MM part allows for the solvent molecules to be polarized by the solute and by interactions with other solvent molecules. Initial applications of the model to calculate the vertical electronic excitation energies and frequency-dependent molecular polarizability of a water molecule in a cluster of 127 classical water molecules are presented. The effect of using different exchange correlation ͑xc͒-potentials is investigated and the results are compared with results from wave function methods combined with a similar solvent model both at the correlated and uncorrelated level of theory. It is shown that accurate results in agreement with correlated wave function results can be obtained using xc-potentials with the correct asymptotic behavior.

Refractive index and third‐order nonlinear susceptibility of C60 in the condensed phase calculated with the discrete solvent reaction field model

“…The (hyper)polarizabilities can be found using response theory in combination with the finite field method [34,35]. We have shown [32] that this approach enables the calculation of different environmental effects in going from microscopic to macroscopic properties.…”

Microscopic and macroscopic polarization within a combined quantum mechanics and molecular mechanics model

“…This is done by replacing the point charge by a Gaussian charge distribution with a unit width and point dipoles smeared out in a similar manner. 18,19,43 In this work we will extend the QM/MM formalism to also include the so-called local field factors, i.e., the difference between the macroscopic electric field and the actual electric field felt by the solute. This will enable the calculation of effective microscopic properties which can be related to the macroscopic susceptibilities.…”

Polarizabilities, Hyperpolarizabilities and Analogous Magnetic Properties

“…Examination of Table 5 and Figure 1 shows that this would imply that the dispersion at the longer wavelength end of the optical range is very small. [44][45][46][47][48][49] for að0Þ are summarized in Table 6. The calculations give the electronic part of the polarizability.…”