A molecular theory of solvation dynamics

Abstract

The dynamic solvation time correlation function 𝒵(t) is, within linear response, formulated in terms of the intermolecular solute–solvent interactions, without recourse to the intrinsically macroscopic concept of a cavity carved out of a dielectric medium. For interaction site models (ISM) of both the solute and the solvent, the theory relates the fluctuating polarization charge density of the solvent to the fluctuating vertical energy gap that controls 𝒵(t). The theory replaces the factual (or bare) solute charge distribution by a surrogate expressed in terms of the solute–solvent site–site direct correlation functions. Calculations for solute ions in water and in acetonitrile lead to 𝒵(t) and the second moment of the associated spectral density in good agreement with molecular dynamics simulation results in the literature. We also use the theory to calculate 𝒵(t) for model solutes in which the ‘‘sudden’’ change of the charge distribution involves multipoles of higher order. The response is qualitatively similar in the various cases studied here.

Distinguishing dynamical features of water inside protein hydration layer: Distribution reveals what is hidden behind the average

“…We have used four spheres situated at different locations inside PHL for each protein to probe the dynamical response of different sites. The interaction energies are taken to be the sum of coulomb and LJ interactions 62 . Linear response theory 63 is applied on each energy trajectory to find out the solvation time correlation function 62,[64][65][66][67] [Equation (15)] and the timescales are obtained using a multi-exponential fitting equation with a Gaussian component to take care of the initial sub ~100 fs ultrafast decay 68 (see Table 8 for details).…”

An advanced continuum medium model for treating solvation effects: Nonlocal electrostatics with a cavity

“…[22][23][24][25][26][27][28][29][30][31][37][38][39][40][41][43][44][45][46][47][48][49][50][51] A nonlocal study of medium effects is a general phenomenological approach which, within the bounds of the linear response approximation, contains any effect occurring at a microscopic level. In this work, we assumed another important approximation: that nonlocal susceptibility integral kernels are isotropic nontensorial quantities.…”

“…[19][20][21][22][23][24][25][26][27][28][29][30][31] The microscopic statistical theory of the structure and dynamics of polar liquids is a field of current research, [32][33][34][35][36][37][38][39][40][41] and has served as the basis for several molecular theories of solvation. [42][43][44][45][46][47][48][49][50][51] Deficiencies in the simple continuum approach were revealed beyond doubt in studies of nonequilibrium time-dependent phenomena, including dielectric relaxation, 25,30,[49][50][51][52][53][54] spectroscopy, [54][55][56] and electron transfer. 30,[57][58][59] The present paper is aimed at a formulation of an impro...…”

Nonlocal continuum solvation model with exponential susceptibility kernels

“…A final comment is concerned with the utility of smooth exponential susceptibility kernels, which seems to contradict the results of recent molecular-level theoretical investigations of the nonlocal dielectric tensor of polar liquids. 5,14,15,17,18,20,27,40,41 Such an approximation appears to work effectively as an empirical tool for treating the solvation energy of ionic species. Note that our fitting of experimental data could be significantly improved by adding extra Lorentzian terms to the susceptibility function ͑4.8͒ ͑Refs.…”

“…The ultimate goal is to get a physically consistent picture of basic solvation properties such as the equilibrium solvation energy of spherical ions. This investigation is motivated by recent developments in molecular solvent models, including computer simulations, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] investigations of pair distribution functions based on solving the integral equations of the theory of liquids [16][17][18][19][20][21] and other molecular theories. 17,[22][23][24][25][26][27][28] The nonlocal theory is based on a linear response relation between the electric field strength vector E(r) and the polarization P(r) ͑where r is a point in space͒:…”