Orientational Isomerism In Water Clusters (H2O)n, n = 2–5, Corresponding to the Complete Set of Oriented Graphs

On the basis of the quantum chemical calculation X3LYP/6-311G++(2d, 2p) for orientational isomers of water clusters (H2O)n, n = 2–5, corresponding to the full set of oriented graphs with the number of vertices ranging from 2 to 5, the thermodynamic functions and cluster concentrations in the gas phase are determined. It is found that for a correct assessment of gas-phase concentrations it is necessary to take into account the phenomenon of orientational isomerism of water clusters. For the full set of orientational isomers, the concentration of water clusters in the gas phase in saturated vapor under standard conditions turns out to be 1–2 orders of magnitude higher than the concentrations calculated only for the lowest energy structures.