A continuum model for solvation effects in binary solvent mixtures is formulated in terms of the ... more A continuum model for solvation effects in binary solvent mixtures is formulated in terms of the density functional theory. The presence of two variables, namely, the dimensionless solvent composition y and the dimensionless total solvent density z, is an essential feature of binary systems. Their coupling, hidden in the structure of the local dielectric permittivity function, is postulated at the phenomenological level. Local equilibrium conditions are derived by a variation in the free energy functional expressed in terms of the composition and density variables. They appear as a pair of coupled equations defining y and z as spatial distributions. We consider the simplest spherically symmetric case of the Born-type ion immersed in the benzene/dimethylsulfoxide (DMSO) solvent mixture. The profiles of y(R) and z(R) along the radius R, which measures the distance from the ion center, are found in molecular dynamics (MD) simulations. It is shown that for a given solute ion z(R) does not depend significantly on the composition variable y. A simplified solution is then obtained by inserting z(R), found in the MD simulation for the pure DMSO, in the single equation which defines y(R). In this way composition dependences of the main solvation effects are investigated. The local density augmentation appears as a peak of z(R) at the ion boundary. It is responsible for the fine solvation effects missing when the ordinary solvation theories, in which z=1, are applied. These phenomena, studied for negative ions, reproduce consistently the simulation results. For positive ions the simulation shows that z>1 (z=5-6 at the maximum of the z peak), which means that an extremely dense solvation shell is formed. In such a situation the continuum description fails to be valid within a consistent parametrization.
ABSTRACT The natural reaction coordinates (NRC) are not well suitable for the dynamical investiga... more ABSTRACT The natural reaction coordinates (NRC) are not well suitable for the dynamical investigation of the transfer of the light atom in chemical exchange reactions. In this case the curvature of the reaction coordinate is large and the probability flux gets across the region of multi-valuedness of the NRC. We introduce a new coordinate system (the matching coordinates, MC), that are specially adapted for the reactions with large curvature, and suggest a new method for solving equations of motion in those coordinates. The multi-valuedness is eliminated by drawing a cut from the centre of maximum curvature of the reaction coordinate curve. Matching of the wavefunction and its normal derivative is performed along the cut. The matching conditions play the role of the operator that is responsible for the direct interaction between the reactant and product regions of a potential energy surface and promotes nonadiabatic transitions between them. The matrix Schrödinger equation for the translational motion is converted into a form that can be solved by the previously elaborated effective procedure. The construction of the scattering matrix for this problem, involving equations of motion with constraints (the matching conditions), needs a special projection technique.
We consider a modified formulation for the recently developed new approach in the continuum solva... more We consider a modified formulation for the recently developed new approach in the continuum solvation theory (Basilevsky, M. V., Grigoriev, F. V., Nikitina, E. A., Leszczynski, J., J. Phys. Chem. B 2010, 114, 2457), which is based on the exact solution of the electrostatic Poisson equation with the space-dependent dielectric permittivity. Its present modification ensures the property curl E =
A continuum model for solvation effects in binary solvent mixtures is formulated in terms of the ... more A continuum model for solvation effects in binary solvent mixtures is formulated in terms of the density functional theory. The presence of two variables, namely, the dimensionless solvent composition y and the dimensionless total solvent density z, is an essential feature of binary systems. Their coupling, hidden in the structure of the local dielectric permittivity function, is postulated at the phenomenological level. Local equilibrium conditions are derived by a variation in the free energy functional expressed in terms of the composition and density variables. They appear as a pair of coupled equations defining y and z as spatial distributions. We consider the simplest spherically symmetric case of the Born-type ion immersed in the benzene/dimethylsulfoxide (DMSO) solvent mixture. The profiles of y(R) and z(R) along the radius R, which measures the distance from the ion center, are found in molecular dynamics (MD) simulations. It is shown that for a given solute ion z(R) does not depend significantly on the composition variable y. A simplified solution is then obtained by inserting z(R), found in the MD simulation for the pure DMSO, in the single equation which defines y(R). In this way composition dependences of the main solvation effects are investigated. The local density augmentation appears as a peak of z(R) at the ion boundary. It is responsible for the fine solvation effects missing when the ordinary solvation theories, in which z=1, are applied. These phenomena, studied for negative ions, reproduce consistently the simulation results. For positive ions the simulation shows that z>1 (z=5-6 at the maximum of the z peak), which means that an extremely dense solvation shell is formed. In such a situation the continuum description fails to be valid within a consistent parametrization.
ABSTRACT The natural reaction coordinates (NRC) are not well suitable for the dynamical investiga... more ABSTRACT The natural reaction coordinates (NRC) are not well suitable for the dynamical investigation of the transfer of the light atom in chemical exchange reactions. In this case the curvature of the reaction coordinate is large and the probability flux gets across the region of multi-valuedness of the NRC. We introduce a new coordinate system (the matching coordinates, MC), that are specially adapted for the reactions with large curvature, and suggest a new method for solving equations of motion in those coordinates. The multi-valuedness is eliminated by drawing a cut from the centre of maximum curvature of the reaction coordinate curve. Matching of the wavefunction and its normal derivative is performed along the cut. The matching conditions play the role of the operator that is responsible for the direct interaction between the reactant and product regions of a potential energy surface and promotes nonadiabatic transitions between them. The matrix Schrödinger equation for the translational motion is converted into a form that can be solved by the previously elaborated effective procedure. The construction of the scattering matrix for this problem, involving equations of motion with constraints (the matching conditions), needs a special projection technique.
We consider a modified formulation for the recently developed new approach in the continuum solva... more We consider a modified formulation for the recently developed new approach in the continuum solvation theory (Basilevsky, M. V., Grigoriev, F. V., Nikitina, E. A., Leszczynski, J., J. Phys. Chem. B 2010, 114, 2457), which is based on the exact solution of the electrostatic Poisson equation with the space-dependent dielectric permittivity. Its present modification ensures the property curl E =
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Papers by M. Basilevsky