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Assessing Many-Body Effects of Water Self-Ions. II: H3O+(H2O)n Clusters

submitted on 02.05.2019, 14:22 and posted on 03.05.2019, 16:04 by Colin K. Egan, Paesani Lab

The importance of many-body effects in the hydration of the hydronium ion (H3O+) is investigated through a systematic analysis of the many-body expansion of the interaction energy carried out at the coupled cluster level of theory for the low-lying isomers of H3O+(H2O)n clusters with n = 1 − 5. This is accomplished by partitioning individual fragments extracted from the whole clusters into “groups” that are classified by both the number of H3O+ and water molecules and the H-bonding connectivity within a given fragment. Effects due to the presence of the Zundel ion, (H5O2)+, are analyzed by further partitioning fragment groups by the “context” of their parent clusters. With the aid of the absolutely localized molecular orbital energy decomposition analysis (ALMO EDA), this structure-based partitioning is found to largely correlate with the character of different many-body interactions, such as cooperative and anticooperative hydrogen-bonding, within each fragment. This analysis emphasizes the importance of a many-body representation of inductive electrostatics and charge transfer in modeling the hydration of an excess proton in water. The comparison between the reference coupled cluster many-body interaction terms with the corresponding values obtained with various exchange-correlation functionals demonstrates that many of these functionals yield an unbalanced treatment of the H3O+(H2O)n configuration space.


National Science Foundation

Air Force Office of Scientific Research


Email Address of Submitting Author


University of California, San Diego


United States

ORCID For Submitting Author


Declaration of Conflict of Interest

No conflict of interest


Read the published paper

in Journal of Chemical Theory and Computation