Аннотация:[Na(H2O)n]+ sodium cation and [Cl(H2O)n]– chloride anion aquacomplexes that involve n ≤ 55 molecules are considered as possible model precursors of instantaneous fragments of aqueous NaCl solutions.As a result of quantum chemical simulations with the use of the density functional approximation witha B3LYP hybrid functional and 6-31G(d,p) extended Gaussian basis set, the structures that mimic localhydration of the ions in the bulk phase and close to the air–solution interfaces are found. Estimated local hydration enthalpies of the ions in combination with the constructed profiles of the van-der-Waals surfaces of the aquacomplexes and the determined connectivity degrees of the hydrogen-bond networks provided grounds for distinguishing configurations that should be most probable in the actual dynamic structure of the solution. At a standard unimolar concentration of a particular ion, a substantial change in the nature and apparent size of the counterion is shown to cause changes in the mean hydration enthalpy of the ion.
