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Updated: Jun 12, 2025
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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
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Low-Energy Isomers of the Magic Number H+(H2O)21 Cluster
T-H Choi1, E V Henderson1, K D Jordan1
1Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States.
The Journal of Physical Chemistry. A
|May 21, 2025
Summary
Researchers explored protonated water clusters, H+(H2O)21, using electronic structure calculations. They identified new low-energy isomers with unique ring structures, including novel 4- and 6-membered rings, impacting cluster stability.
Area of Science:
- Computational Chemistry
- Physical Chemistry
- Materials Science
Background:
- Protonated water clusters are fundamental to understanding proton transport in aqueous systems.
- The pentagonal dodecahedron is a common structural motif for (H2O)20 clusters.
- The localization of excess protons significantly influences the stability and structure of water clusters.
Purpose of the Study:
- To characterize low-energy isomers of the protonated water cluster H+(H2O)21.
- To investigate the structural and energetic impact of an internal water molecule on cluster stability.
- To identify novel ring configurations within the cluster, particularly those involving 4- and 6-membered rings.
Main Methods:
- Utilized electronic structure calculations to perform theoretical characterization.
- Focused on isomers based on the (H2O)20 pentagonal dodecahedron framework.
- Analyzed proton localization on the surface and the position of an additional water molecule in the interior.
Main Results:
- Identified eleven distinct classes of low-energy isomers for H+(H2O)21.
- In most isomers, the internal water molecule forms six 5-membered rings.
- A novel isomer with a 4-membered ring (and additional 6- and 5-membered rings) was found to be energetically close (0.6 kcal/mol) to the global minimum. Isomers with two 4- and two 6-membered rings on the surface were also identified at a similar energy (∼1.3 kcal/mol).
Conclusions:
- The energetic landscape of H+(H2O)21 is complex, with several low-energy isomers.
- The formation of 4- and 6-membered rings significantly impacts cluster stability.
- These findings provide insights into proton dynamics and structural variations in hydrated proton systems.
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