Free-energy molecular simulations of the inclusion complex of Ne with fullerene C60 in water

Abstract

Binding free energy of Ne in the endohedral fullerene Ne@C60 in water was calculated using closed thermodynamic cycle that involves annihilation in silico of Ne in the free and bound states. The underlying microscopic force field molecular dynamics simulations were performed at 300 K in the constant-volume 27.9 Å periodic box of the TIP3P water molecules. The reference binding free energy of a dummy atom to C60 was calculated from the ideal gas theory equations. The free energies of atom annihilation were computed by means of the free-energy perturbation and Bennett acceptance ratio methods. Introduction of intermediate particle of small size in the mutation scheme in C60 substantially improved free-energy convergence. The predicted binding free energies of Ne and Ne cavity to C60 at the standard state concentration are about − 5 kJ mol− 1 and +22 kJ mol− 1, respectively. The free energy of reversible annihilation of Ne is controlled by the insertion step for simulations both in water and in C60.