Hydronium ions proton solvation models

In some circunstances, it might be convenient to take the hydronium ion as the basic unit for a proton in solution. In those cases, what is needed is the hydronium solvation free energy, AG° i (HgO ). Table VII.IO shows the results of theoretical calculations (da Silva [44b]), unless otherwise speci-hed) obtained with different continuum solvation models, according to the Ben-Naim [106] definition of the solvation process. Note that the only experimental value available (Pearson [107]) was obtained assuming AG/oi (H ) = —259.5 kcal/mol, which differs considerable from the more recent experiments of Tissandier et al. [104]. However, if one adopts Tissandier s result for the proton solvation energy, Pearson s scheme furnishes AG/oi (H30 ) = —106.16 kcal/mol, a value in close agreement with some of the theoretical results shown in Table VII.IO. 

The solvation structure of the proton was taken into account by modeling it as a solvated hydronium ion H30+(H20)2. Ab initio SCF-HF MP2 theory was used along with small Pt atom clusters to show that the dissociative adsorption of H2O requires the direct assistance of additional H2O molecules ... 

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