Computational modelling for the clustering degree in the saturated steam and the water-containing complexes in the atmosphere

Recent computational findings of temperature increase of clustering degree in several quite different saturated vapors are analyzed further. A thermodynamic proof is presented, showing that this event should be rather common, if not general. Illustrations are based on the saturated steam and consequences for the atmosphere are discussed with both homo- and hetero-clustering. MP2=FC/6-311G** results for the H2O·N2 (the best stabilization energy -1.62kcal/mol, which corresponds to -1.44kcal/mol with the G3 theory) and H2O·O2 (the best stabilization energy -0.96kcal/mol) hetero-dimers, and the G1-theory (O2)2 data (the best stabilization energy -0.62kcal/mol) are reported. The water-dimer thermodynamics is recomputed in an anharmonic regime and a remarkable agreement with experiment is found. The results have some significance for the atmospheric greenhouse effect.