Choice of the center of water molecules in calculations of partial molar volume of single ions immersed in water: A molecular simulation study

Abstract

In the Kirkwood–Buff theory, the center of each solvent molecule can be arbitrarily chosen. However, this arbitrariness is not obvious in the calculation of the Kirkwood–Buff integral for a single ion. Actually, the Kirkwood–Buff integral depends on the choice of the center of a solvent molecule, if each solvent molecule has a dipole moment and the solute has a net charge. A few examples based on molecular dynamics simulations are shown. A surrogate definition for the center of a water molecule is also shown. A good agreement between the calculated and experimental values of partial molar volumes for single ions is observed.