Lg. Gorb et al., MNDO-PM3 INVESTIGATION OF MOLECULE AND ION HYDRATION .1. GEOMETRY ANDTHERMODYNAMICS OF H(H2O)(N)(+) WATER CLUSTERS, Journal of molecular structure. Theochem, 331(3), 1995, pp. 235-244
Quantum-chemical calculations of the energy, electronic structure and
thermodynamics of H(H2O)(n)(+) hydrated clusters have ben performed by
the MNDO-PM3 semiempirical method. It was determined that when n is s
mall H(H2O)(n)(+) ions have the hydrated H3O+ geometry. When the numbe
r of water molecules increases to five each cluster can be both hydrat
ed H3O+ and H5O2+ structures. However, the hydration of the H3O+ ion i
s energetically preferable. The calculated values of stepwise hydratio
n entropy are in fair correspondence with experiment. Nevertheless, th
e entropy analysis does not allow distinction to be made between hydra
ted H3O+ and H5O2+ ions because both isometric types have close Delta
S-n-1,n(o) values and close translation, rotation and vibration compon
ents.