Theoretical Basis for the Treatment of Solvent Effects in the Context of Density Functional Theory (original) (raw)
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Physical Review E, 2002
In the density functional theory formulation of molecular solvents, the solvation free energy of a solute can be obtained directly by minimization of a functional, instead of the thermodynamic integration scheme necessary when using atomistic simulations. In the homogeneous reference fluid approximation, the expression of the free-energy functional relies on the direct correlation function of the pure solvent. To obtain that function as exactly as possible for a given atomistic solvent model, we propose the following approach: first to perform molecular simulations of the homogeneous solvent and compute the position and angle-dependent two-body distribution functions, and then to invert the Ornstein-Zernike relation using a finite rotational invariant basis set to get the corresponding direct correlation function. This rather natural scheme is proved, for the first time to our knowledge, to be valuable for a dipolar solvent involving long range interactions. The resulting solvent free-energy functional can then be minimized on a three-dimensional grid around a solute to get the solvent particle and polarization density profiles and solvation free energies. The viability of this approach is proven in a comparison with ''exact'' molecular dynamics calculations for the simple test case of spherical ions in a dipolar solvent.
Tackling solvent effect by coupling electronic and molecular Density Functional Theory
2020
Solvation effect might have a tremendous influence on chemical reactions. However, precise quantum chemistry calculations are most often done either in vacuum neglecting the role of the solvent or using continuum solvent model ignoring its molecular nature. We propose a new method coupling a quantum description of the solute using electronic density functional theory with a classical grand-canonical treatment of the solvent using molecular density functional theory. Unlike previous work, both densities are minimized self consistently, accounting for mutual polarization of the molecular solvent and the solute. The electrostatic interaction is accounted using the full electron density of the solute rather than fitted point charges. The introduced methodology represents a good compromise between the two main strategies to tackle solvation effect in quantum calculation. It is computationally more effective than a direct quantum-mechanics/molecular mechanics coupling, requiring the explo...
Continuum Solvation Models in Chemical Physics: From Theory to Application
We review the field of computational studies of photochemistry in condensed phases, with particular emphasis on the nonadiabatic dynamics of excited states. We examine methods for the determination of potential energy surfaces (PES) and other electronic properties in large systems, from clusters to liquids and crystals. The change of the PES with respect to the isolated molecule case is the most important item of the "static" environmental effects in photochemistry. "Dynamic" effects mainly consist in the transfer of energy and momentum from the chromophore or reactive center to the surrounding molecules. The interplay of internal processes, including the photoreaction, with thermalization and other more specific effects of chemical environment, can hardly be analyzed without the help of simulations of the excited state dynamics. A survey of methods and applications shows advantages and weaknesses of the basic choices offered by the state of the art: quantum wavepacket versus trajectory approaches, direct versus two-step dynamics, continuum versus explicit representations of the solvent.
Classical density functional theory to tackle solvation in molecular liquids
arXiv: Chemical Physics, 2015
We present a brief review of the classical density functional theory of atomic and molecular fluids. We focus on the application of the theory to the determination of the solvation properties of arbitrary molecular solutes in arbitrary molecular solvent. This includes the prediction of the solvation free energies, as well as the characterization of the microscopic, three-dimensional solvent structure.
Biophysical Chemistry, 1994
An attempt is made to combine continuum reaction field approaches with DIT ab initio calculations for quantitative evaluation of solvation effects in chemical processes. The formalism of the combined method is delineated along with its possibilities and limitations, and applied to several small model systems. It is found that DFT can provide dipole moments in vacuum and in solution (e.g., for water) with accuracies (0.1 D) that have not been reported with other methods. The results obtained suggest that agreement within -1 kcal/mole can be expected between calculated and experimental hydration enthalpies of polar uncharged solutes. The results for ions are not as consistent as for dipolar molecules, suggesting that accurate multipole representations of the electron density of solutes may be required especially for ionic solutes.
Journal of Computational Chemistry, 1991
We report a systematic comparison of the dispersion and repulsion contributions to the free energy of solvation determined using quantum mechanical self-consistent reaction field (QM-SCRF) and classical methods. In particular, QM-SCRF computations have been performed using the dispersion and repulsion expressions developed in the framework of the integral equation formalism of the polarizable continuum model, whereas classical methods involve both empirical pairwise potential and surface-dependent approaches. Calculations have been performed for a series of aliphatic and aromatic compounds containing prototypical functional groups in four solvents: water, octanol, chloroform, and carbon tetrachloride. The analysis is focused on the dependence of the dispersion and repulsion components on the level of theory used in QM-SCRF computations, the contribution of those terms in different solvents, and the magnitude of the coupling between electrostatic and dispersion-repulsion components. Finally, comparison is made between the dispersion-repulsion contributions obtained from QM-SCRF calculations and the results determined from classical approaches.
Chemical Physics, 1993
A configuration interaction (CI) version of the self-consistent reaction field theory is formulated in order to treat solvation problems in the framework of the continuum medium model. The problem of an optimal selection of the truncated conligurational basis set for large molecular solutes is considered. For the description of solvation effects most important are found to be the charge transfer electronic configurations which can be treated on the background of incompletely convergent total CI expansions because the contributions of local excitations are mutually canceled with a high accuracy under the conditions of a solvent effect calculation.
Solvation energies from the linear response function of density functional theory
Chemical Physics Letters, 1996
Starting from a local approximation to the softness kernel proposed by Vela and Gfisquez [J. Am. Chem. Soc. 112 (1990) 1490], a useful equation for the solvation energy is derived. The resulting expression contains a first order contribution representing the electrostatic solute-solvent interaction energy, and a second order term associated to the fluctuation of the reaction field potential as electrons are added to the solute system. The most relevant result of the present formalism is that the solvation energy displays a linear dependence on the global softness. This expression is tested for a series of atomic and molecular systems.