Cluster Formation at Extreme Supersaturations: Nucleation versus Barrierless Transition

Area of Science:

• Physical Chemistry
• Chemical Physics
• Thermodynamics

Background:

• Cluster formation is crucial in phase transitions.
• Extreme supersaturation conditions alter nucleation kinetics.
• Evaporation significantly impacts cluster dynamics.

Purpose of the Study:

• Identify conditions for barrierless cluster formation.
• Investigate the role of kinetics in nucleation.
• Analyze water nucleation in Laval nozzle experiments.

Main Methods:

• Applied coalescence equation for cluster size distribution.
• Utilized pressure-temperature-dependent association coefficients (k_).
• Compared free molecular collision model with ab initio calculations for k_.

Main Results:

• Defined a temperature-supersaturation domain for barrierless nucleation.
• Found theoretical nucleation rates agree well with experiments.
• Observed discrepancies in small cluster densities.

Conclusions:

• Ab initio calculations for association coefficients are vital for accurate nucleation predictions.
• Discrepancies suggest limitations in experimental k _{extraction or ab initio models.}
• Further refinement of kinetic models is needed for precise cluster density predictions.