Molecular dynamics of evaporative cooling of water clusters

The cooling of water clusters through evaporation into a vacuum is studied using classical molecular dynamics with the SPC water model, and the results are compared with macroscopic theory. A simple model based on the Hertz-Knudsen equation significantly underestimates cooling rates. A modified approach that accounts for the Kelvin equation provides better results. Further insight is gained by comparing temperatures derived from different degrees of freedom. While the rotational temperature of the clusters is only slightly lower than their internal temperature and decreases over time, the translational temperature of the clusters, considered as individual particles, remains nearly unchanged.