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Updated: Dec 28, 2025

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Intramolecular Reactions in Ionized Ammonia Clusters: A Direct Ab Initio Molecular Dynamics Study
1Division of Applied Chemistry, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
Ammonia cluster cations exhibit two reaction pathways: proton transfer and complex formation. Proton transfer occurs in all clusters, while complex formation is observed in larger ones, offering insights into astrochemical reactions.
Area of Science:
- Astrochemistry
- Chemical Physics
- Materials Science
Background:
- Ammonia cluster cations are crucial in planetary atmospheres and materials chemistry.
- Their reactivity as super-alkali species is of recent research interest.
Purpose of the Study:
- Investigate reactions of ammonia cluster cations [(NH3)n]+ (n=2-6) after ionization.
- Elucidate reaction mechanisms under astrochemical conditions using theoretical calculations.
Main Methods:
- Direct ab initio molecular dynamics simulations.
- Analysis of competing proton transfer and complex formation channels.
Main Results:
- Proton transfer (PT) observed in all clusters (n=2-6), accelerating with size.
- Complex formation (N-N bond) observed in larger clusters (n=5-6).
- PT and complex formation time scales are 20-30 fs and 40-50 fs, respectively.
Conclusions:
- Two distinct reaction channels govern ammonia cluster cation behavior post-ionization.
- Cluster size significantly influences the prevalence and kinetics of these reaction pathways.
- Findings provide theoretical insights into ammonia cluster cation reactions in astrochemical environments.
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