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Updated: Sep 5, 2025
12:11
Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
8.3K
Nonisothermal nucleation in the gas phase is driven by cool subcritical clusters
Valtteri Tikkanen1, Bernhard Reischl1, Hanna Vehkamäki1
1Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki FI-00014, Finland.
Summary
Gas phase nucleation is complex. This study reveals that while latent heat release can elevate cluster temperatures, nucleation rates are only moderately suppressed, with critical clusters warming as they grow.
Area of Science:
- Physical Chemistry
- Thermodynamics
- Statistical Mechanics
Background:
- Gas phase nucleation is a fundamental process in first-order phase transitions.
- Classical nucleation theory often assumes isothermal conditions, neglecting latent heat release.
- The impact of non-isothermal effects on nucleation dynamics and rates remains a subject of debate.
Purpose of the Study:
- To investigate the non-isothermal dynamics and energetics of homogeneous nucleation.
- To understand how released latent heat affects cluster temperatures and nucleation rates.
- To compare simulation results with existing kinetic modeling and classical non-isothermal theories.
Main Methods:
- Molecular dynamics simulations of supersaturated vapor with a thermalizing carrier gas.
- Analysis of cluster temperatures and nucleation rates.
- Comparison with isothermal nucleation models and classical non-isothermal nucleation theory.
Main Results:
- Nucleation rates are suppressed by at most two orders of magnitude, despite significant latent heat release.
- Cluster temperatures within the entire size population are elevated.
- Clusters driving the nucleation flux transition from cold to hot as they grow from subcritical to supercritical sizes.
Conclusions:
- Non-isothermal effects moderately suppress nucleation rates in the studied systems.
- The temperature evolution of critical clusters resolves apparent contradictions in previous theoretical considerations.
- Provides crucial insights into realistic nucleation events and validates/challenges existing theories.
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