The ubiquity of water is shared with its self-ions, H3O+ and OH−, which function as the mediators of aqueous acid/base chemistry, and therefore have a fundamental role in many scientific and technological applications. In order to develop a cohesive picture of the interactions present in these systems, we conducted a detailed investigation of many-body effects in low-energy H3O+(H2O)n and OH−(H2O)n (n ≤ 5) clusters at the CCSD(T) level of theory, extrapolated to the complete basis set limit. Note that the rapid convergence of each system's respective many-body expansion suggests that analysis of small clusters can be extended to bulk aqueous phases. Informed by our knowledge of cooperative and anticooperative effects in neutral water, we organized cluster fragments into groups based on their directional hydrogen bonding connectivity, and found that the connectivity of a given fragment consisting of K monomers often indicates whether the K-body energy of that K-mer is attractive or repulsive. To gain further insight into the nature of these interactions, we decomposed the 3B energies of significant 3-mer fragment groups using the absolutely localized molecular orbital energy decomposition analysis (ALMO EDA) method, which identified the importance of 3B polarization and charge transfer. Finally, we evaluated the performance of various exchange-correlation (density) functionals in reproducing 2B and 3B interaction energies of significant 2- and 3-mer fragment groups.

Many-body effects in protonated and deprotonated water clusters

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.