Solvation of two-dimensional Lennard-Jones solutes. Thermodynamic perturbation theory and Monte Carlo simulations

We study the transfer of two- dimensional Lennard-Jones solutes into the two-dimensional Lennard-Jones solvent. Thermodynamic quantities associated with this process are calculated. For this purpose the Monte Carlo method in two different ensembles, reflecting different thermodynamic restrictions, is utilized. The excess free enthalpy, excess enthalpy (p,T), and excess free energy and excess internal energy (V,T) of the transfer of a solute into the solvent are calculated. In addition to the Monte Carlo method the thermodynamic perturbation theory is applied to the same system. The necessary expressions to calculate the transfer properties within the thermodynamic perturbation theory are derived. The theoretical results are tested against the Monte Carlo computer simulations. Very good agreement between the thermodynamic perturbation theory results and exact computer simulations is obtained. These results lend some confidence into the thermodynamic perturbation theory and suggests its application to more realistic systems.