Free energy perturbation and dynamical nucleation study of water dimer and trimer through TIP5P water model

Classical potential of mean forces as a function of reaction coordinate of dimer and trimer were calculated from molecular dynamic simulation based on the recently developed TIP5P water model. Ab initio/classical free energy perturbation method (ABC-FEP) was applied to these classic model potential to get quantum corrected potential. Variational transition state theory gives a prescription for defining a unique location of dividing surface for each reaction. The critical radius of the cluster, rcut, was found through the minimum value of −exp(−βA(r))dA(r)/dr. And this upper bound to the evaporation rate constant krcutTST is related to Helmholtz free energy and potential of mean force. The equilibrium constant and condensation rate constant for both classical model and ABC-FEP model were calculated based on water dimer and trimer.