CALCULATION OF PARTIAL MOLAR VOLUME AND ITS COMPONENTS FOR MOLECULAR DYNAMICS MODELS OF DILUTE SOLUTIONS
N. N. Medvedev1,2, V. P. Voloshin1, A. V. Kim1, A. V. Anikeenko1, A. Geiger3
1V. V. Voevodskii Institute of Chemical Kinetics and Combustion, Siberian Division, Russian Academy of Sciences, Novosibirsk
2Novosibirsk State University, Novosibirsk
3Technical University of Dortmund, Dortmund, Germany
Keywords: solutions, partial molar volume, intrinsic volume, molecular dynamics simulation, Voronoi–Delaunay method
Abstract
This paper is a review of our recent computational studies of volumetric characteristics using computer models of dilute solutions. Partial molar volume (PMV) and its components are calculated for simple and complex molecules in water (methane, noble gases, surfactants, polypeptides). Advantages and disadvantages of various computational methods are discussed. It is proposed to use the Voronoi–Delaunay technique to determine the reasonable boundary between a solute molecule and solvent molecules and to identify the PMV components related to the molecule, the boundary layer, and the solvent. It is noted that the observed increase in PMV with temperature for large molecules is due to an increase in the volume of voids in the boundary layer, i.e., due to the “thermal volume”. In this case, the solvent gives a negative contribution to the PMV. In contrast, for simple molecules (methane), the contribution from the solvent is positive and is the main factor in the increase in the PMV, which is associated with a specific change in water structure around a spherical hydrophobic particle outside the boundary layer. For surfactant molecules, the contribution from the solvent changes sign (from negative to positive) with increasing temperature.
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