Structure and Thermodynamics of H3O+(H2O)8 Clusters: A Combined Molecular Dynamics and Quantum Mechanics Approach
Temelso, B.; Köddermann, T.; Kirschner, K. N.; Klein, K.; Shields, G. C. Structure and Thermodynamics of H3O+(H2O)8 Clusters: A Combined Molecular Dynamics and Quantum Mechanics Approach. Comput. Theor. Chem. 2013, 1021, 240-248.
We have studied the structure and stability of H3O+(H2O)8 clusters using a combination of molecular dynamics sampling and high-level ab initio calculations. 20 distinct oxygen frameworks are found within 2 kcal/mol of the electronic or standard Gibbs free energy minimum. The impact of quantum zero-point vibrational corrections on the relative stability of these isomers is quite significant. The box-like isomers are favored in terms of electronic energy, but with the inclusion of zero-point vibrational corrections and entropic effects tree-like isomers are favored at higher temperatures. Under conditions from 0 to 298.15 K, the global minimum is predicted to be a tree-like structure with one dangling singly coordinated water molecule. Above 298.15 K, higher entropy tree-like isomers with two or more singly coordinated water molecules are favored. These assignments are generally consistent with experimental IR spectra of (H3O+)(H2O)8 obtained at ∼150 K.
Computational and Theoretical Chemistry