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 k r cut TST 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.