A molecular dynamics study of the evolution from the formation of the C6F6 –(H2O)n small aggregates to the C6F6 solvation

The interaction between hexafluorobenzene, C6F6, and H2O is investigated to construct a force field for molecular dynamics simulations. In order to construct the C6F6-H2O intermolecular interaction function, the non-permanent charge contributions, grouped in the so-called nonelectrostatic term and described using an improved Lennard-Jones model, are combined with the electrostatic energy calculated in agreement with the permanent electric quadrupole and dipole moments of C6F6 and H2O, respectively. Moreover, to test the potential energy function, BSSE-corrected energies at CCSD(T)/aug-cc-pVTZ level are calculated for three different approaches of H2O-C6F6. By using the constructed force field, the structure and energetics of some small aggregates [C6F6-(H2O)(n) (n = 1-6)], the formation of the first solvation shell [C6F6-(H2O)(n) (n = 9-36)] and the solvation of C6F6 by 400 molecules of H2O have been investigated. The C6F6-(H2O)(n) (n = 1-6) small aggregates and the formation of the first solvation shell have been simulated using a microcanonical (NVE) ensemble of particles, while an isobaric-isothermal ensemble (NpT) has been used to investigate the solvation of C6F6. Moreover, in order to approximate the system formed by one C6F6 and 400 H2O molecules to a large (infinite) system, periodic boundary conditions have been imposed in the simulation of the solvation of C6F6.