Dynamics of Capillary Drying in Water

We use atomistic simulations to address the question when capillary evaporation of water confined in a hydrocarbonlike slit is kinetically viable. Activation barriers and absolute rates of evaporation are estimated using open ensemble Monte Carlo–umbrella sampling and molecular dynamics simulations. At ambient conditions, the evaporation rate in a water film four molecular diameters thick is found to be of the order ${10}^5({\mathrm{n}\mathrm{m}}^2\mathrm{s}{)}^{-1}$, meaning that water readily evaporates. Films more than a few nanometers thick will persist in a metastable liquid state. Dissolved atmospheric gas molecules do not significantly decrease the activation barrier.