Potential energy surface hydronium ions

There is another minimum on the potential energy surface of the (H20)3HC1 trihydrate corresponding to an ionic form of the cluster. The ionic minimum is characterized by a cyclic structure with the Cl ion hydrogen-bonded simultaneously to the two water molecules and the hydronium ion. It is interesting to note that the ionic form is less stable, as it is located 5.2kcal/mol above the neutral minimum. Therefore, the ionic structure of the trihydrate observed in the X-ray experiments 397 cannot directly be related to this ionic minimum. In fact, the structure observed in crystals must be considered as effective, taking into account the crystal field effects. 

In this treatment, the potential energies of the initial state, where the transferring proton is in the solution as a hydronium ion (H30 )and in the final state as an adsorbed hydrogen atom on the metal surface, were given... 

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