Activation energies and potentials of mean force for water cluster evaporation

Activation energies for water cluster evaporation are of interest in many areas of chemical physics. We present the first computation of activation energies for monomer evaporation of small water clusters using the formalism of dynamical nucleation theory (DNT). To this end, individual evaporation rate constants are computed for water clusters (H(2)O)(i), where i=2-10 for temperatures ranging from 243 to 333 K. These calculations employ a parallel sampling technique utilizing a Global Arrays toolkit. The resulting evaporation rate constants for each cluster are then fitted to Arrhenius equations to obtain activation energies. We discuss DNT evaporation rate constants and their relation to potentials of mean force, activation energies, and how to account for nonseparability of the reaction coordinate in the reactant state partition function.