Modeling Solvatochromic Shifts Using the Orbital-Free Embedding Potential at Statistically Mechanically Averaged Solvent Density

Abstract

The correspondence between the exact embedding potential and the pair of the electron densities--that of the embedded molecule and that of its environment [Wesolowski and Warshel, J. Phys. Chem. 1993, 97, 8050]--is used to generate the average embedding potential and to subsequently calculate the solvatochromic shifts in a number of organic chromophores in solvents of various polarities. The averaged embedding potential is evaluated at a fictitious electron density of the solvent, which is obtained by means of "dressing up" with electrons the classical site distributions derived from the statistical-mechanical, 3D molecular theory of solvation (aka 3D-RISM method) [Kovalenko In Molecular Theory of Solvation; Hirata, Ed.; Understanding Chemical Reactivity; 2003, Vol 24], self-consistently coupled with the electronic structure of the solute. The proposed approach to modeling solvatochromic shifts can be situated between the implicit and explicit type of models for the solvent. Numerical examples are given for the lowest-lying n --> pi* and pi --> pi* excitations.

Nonuniform Continuum Model for Solvatochromism Based on Frozen‐Density Embedding Theory

“…Such use of an FDET equation was introduced in Ref. [22] and comprehensively benchmarked in Ref. [23] for modeling solvatochromism of absorption.…”

“…In the present work, we use another procedure to obtain the average quantities 1 B ðrÞ h i and u B ðrÞ h i, which have been previously applied. [22,23] The procedure is based on classical statistical theory of liquids. In the first step, the 3D-RISM equations [19] with Hirata-Kovalenko closure [20] are used to obtain the site probabilities, that is, the probability of finding a particular atom in a given volume element, which is a function in R 3 .…”

“…The details of this procedure are given in Refs. [22,23]. Here, we underline that in the applied procedure, the 3D-RISM and FDET equations are coupled in a self-consistent manner.…”

“…In fact, some decomposition schemes (Mulliken charges for instance) led to numerical instabilities in FDET/3D-RISM studies of solvatochromism in absorption. [22] The procedure based on multipole derived atomic charges was chosen, because of its numerical robustness. [22] The second complication concerns the physicochemical properties of the chromophore, the effect of the environment on both the structure and the charge distribution of the chromophore in its excited state.…”

“…Kovalenko and Hirata [19,20] formulated a self-consistent combination of 3D-RISM with Kohn-Sham density functional theory (DFT) [21] methods. Kaminski et al [22] adopted the same approach to generate the average positive (nuclei) and negative (electrons) charge densities as input quantities for frozen-density embedding theory (FDET) based calculations of solvatochromic shifts in absorption. A comprehensive overview of the performance of such combination is provided in Ref.…”