Using the dielectrically consistent reference interaction site model (DRISM) of molecular solvation, we have calculated structural and thermodynamic information of alkali-halide salts in aqueous solution, as a function of salt concentration. The impact of varying the closure relation used with DRISM is investigated using the partial series expansion of order-n (PSE-n) family of closures, which includes the commonly used hypernetted-chain equation (HNC) and Kovalenko-Hirata closures. Results are compared to explicit molecular dynamics (MD) simulations, using the same force fields, and to experiment. The mean activity coefficients of ions predicted by DRISM agree well with experimental values at concentrations below 0.5 m, especially when using the HNC closure. As individual ion activities (and the corresponding solvation free energies) are not known from experiment, only DRISM and MD results are directly compared and found to have reasonably good agreement. The activity of water directly estimated from DRISM is nearly consistent with values derived from the DRISM ion activities and the Gibbs-Duhem equation, but the changes in the computed pressure as a function of salt concentration dominate these comparisons. Good agreement with experiment is obtained if these pressure changes are ignored. Radial distribution functions of NaCl solution at three concentrations were compared between DRISM and MD simulations. DRISM shows comparable water distribution around the cation, but water structures around the anion deviate from the MD results; this may also be related to the high pressure of the system. Despite some problems, DRISM-PSE-n is an effective tool for investigating thermodynamic properties of simple electrolytes.
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http://dx.doi.org/10.1063/1.4775743 | DOI Listing |
J Phys Condens Matter
September 2016
Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan.
For neutral hard-sphere solutes, we compare the reduced density profile of water around a solute g(r), solvation free energy μ, energy U, and entropy S under the isochoric condition predicted by the two theories: dielectrically consistent reference interaction site model (DRISM) and angle-dependent integral equation (ADIE) theories. A molecular model for water pertinent to each theory is adopted. The hypernetted-chain (HNC) closure is employed in the ADIE theory, and the HNC and Kovalenko-Hirata (K-H) closures are tested in the DRISM theory.
View Article and Find Full Text PDFJ Phys Chem B
October 2014
National Institute for Nanotechnology, National Research Council of Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada.
We present a method of DPD simulation based on a coarse-grained effective pair potential obtained from the DRISM-KH molecular theory of solvation. The theory is first used to calculate the radial distribution functions of all-atom solute monomers in all-atom solvent and then to invert them into an effective pair potential between coarse-grained beads such that their fluid without solvent accounts for molecular specificities and solvation effects in the all-atom system. Bonded interactions are sampled in relatively short MD of the all-atom system and modeled with best multi-Gaussian fit.
View Article and Find Full Text PDFJ Chem Phys
January 2013
Department of Chemistry and Chemical Biology and BioMaPS Institute, Rutgers University, Piscataway, New Jersey 08854, USA.
Using the dielectrically consistent reference interaction site model (DRISM) of molecular solvation, we have calculated structural and thermodynamic information of alkali-halide salts in aqueous solution, as a function of salt concentration. The impact of varying the closure relation used with DRISM is investigated using the partial series expansion of order-n (PSE-n) family of closures, which includes the commonly used hypernetted-chain equation (HNC) and Kovalenko-Hirata closures. Results are compared to explicit molecular dynamics (MD) simulations, using the same force fields, and to experiment.
View Article and Find Full Text PDFPhys Chem Chem Phys
February 2008
Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, D-93040 Regensburg, Germany.
We present a symmetry-reduced version of the dielectrically-consistent reference interaction site model (DRISM) equation and an adaptation of the Labík-Malijevský-Vonka hybrid algorithm for its numerical solution. This approach is used for the calculation of site-site correlation functions of water, acetone and a water-acetone mixture. Compared to the traditional Picard iteration of non-reduced DRISM theories, savings of more than 90% in computational time are obtained.
View Article and Find Full Text PDFBiopolymers
September 1999
Department of Chemistry, University of Houston, Houston, TX 77204-5641, USA.
The structural and dynamical features of the hormone alpha-MSH in solution have been examined over a 100 ns time scale by using free energy molecular mechanics models at room temperature. The free energy surface has been modeled using methods from integral equation theory and the dynamics by the Langevin equation. A modification of the accessible surface area friction drag model was used to calculate the atomic friction coefficients.
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