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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
(H2O)20 water clusters at finite temperatures
P Parkkinen1, S Riikonen, L Halonen
1Laboratory of Physical Chemistry, Department of Chemistry, University of Helsinki , P.O. Box 55, FI-00014 Helsinki, Finland.
The Journal of Physical Chemistry. A
|June 5, 2013
Summary
Free energy terms critically influence water cluster structures. Vibrational and proton disorder effects favor polyhedral shapes, counteracting destabilizing dispersion forces in (H2O)20 clusters.
Area of Science:
- Physical Chemistry
- Computational Chemistry
- Spectroscopy
Background:
- Water clusters are fundamental models for understanding hydrogen bonding in condensed phases.
- The energetic contributions governing cluster stability and dynamics are complex and not fully understood.
Purpose of the Study:
- To investigate the role of various free-energy terms in the stability and distribution of (H2O)20 clusters.
- To analyze the impact of these energetic contributions on the infrared spectrum of water clusters at finite temperatures.
- To develop new energy expressions for prismatic water clusters based on hydrogen-bond connectivity.
Main Methods:
- Comprehensive computational study of energetics for (H2O)20 clusters.
- Analysis of electronic ground-state energy, dispersion interactions, vibrational zero-point corrections, vibrational entropy, and proton configurational entropy.
- Development of energy expressions incorporating hydrogen-bond connectivity parameters.
Main Results:
- Dispersion interactions destabilize polyhedral water clusters.
- Vibrational terms (zero-point and entropic) and proton disorder entropy favor polyhedral structures over compact motifs like prisms.
- A delicate balance exists between different energetic contributions.
- Developed novel energy expressions for prismatic water clusters.
Conclusions:
- Free-energy terms play a crucial role in determining the structural distribution of water clusters.
- The findings provide insights into the behavior of water and ice systems.
- The developed energy expressions offer a new tool for analyzing water cluster energetics.
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