The chemical potential of a dipole in dipolar solvent at infinite dilution: Mean spherical approximation and Monte Carlo simulation

Abstract

A new analytical expression was derived for the chemical potential of a hard sphere dipole in hard sphere dipole fluid at infinite dilution of the solute using the mean spherical approximation (MSA). A set of Monte Carlo (MC) simulations has been carried out to investigate the scope of applicability of the derived equation. The mean reaction field (MRF) approach was used in our MC computations. Two different MC methods (Widom particle insertion and thermodynamic integration) were applied for obtaining the chemical potential change associated with the dipole creation at the solute particle to provide adequate accuracy of the MC simulations. Also, corresponding changes in the mean potential energy were calculated by direct method and by thermodynamic integration. The solvation energies have been obtained for the systems of dipolar hard spheres with reduced dipole moment 1.0 at the reduced densities 0.2, 0.5, and 0.8. Computations have been made for solute particles with the reduced dipole moment varied from 0.0 to 1.5 and the hard sphere diameter varied from 0.5 to 2.0. The variation of those quantities with the molecular parameters was analyzed and compared with the MSA equation and Kirkwood classical expressions. It was found that the MSA calculations agree relatively well with MC simulations at densities less than 0.5 and solute dipole moment less than 1.0.