Size and topology of molecular clusters in supercritical water: a molecular dynamics simulation

A hybrid criterion of hydrogen bonding is applied to the analysis of molecular dynamics trajectories simulated for several near- and supercritical thermodynamic conditions. Even at vapor-like densities supercritical water is shown to contain large molecular clusters, consisting of up to 10 molecules. Relative abundances of topologically different trimers, tetramers, and pentamers are examined, and chain-like clusters are found predominant under supercritical conditions. In contrast to the results of quantum-chemical calculations for isolated water clusters, ring-like clusters are only rarely formed in supercritical water.