DISTANCE DEPENDENCE OF WATER-STRUCTURE AROUND MODEL SOLUTES

Structural peculiarities of water at different distances from model so lute molecules are studied using molecular dynamics simulations. Water structure has been analyzed in five spherical layers around methane a nd ammonium ion using statistical geometry approach and more conventio nal structural descriptors. Distance dependence of water structure is better reflected by the tetrahedrality of Delaunay simplexes and angul ar orientation of water molecules with respect to the solute rather th an by distributions of hydrogen bond distances, angles, and engergies. Both solutes strongly influence water struture in the first hydration shell, and structural properties of water beyond the second solvation shell are similar to those of bulk water. These results suggest that water in simulations of solutions may be represented by explicit model s near solutes and by continuum models in bulk regions.