Argon nucleation: bringing together theory, simulations, and experiment

Area of Science:

• Physical Chemistry
• Computational Physics
• Chemical Engineering

Background:

• Vapor-to-liquid nucleation is a fundamental process in physical chemistry.
• Existing theoretical models and simulation methods for argon nucleation have not been comprehensively compared.
• Discrepancies exist between experimental and theoretical/simulation data for argon nucleation.

Purpose of the Study:

• To provide an overview of experimental, theoretical, molecular dynamics (MD), and density functional theory (DFT) studies of argon vapor-to-liquid nucleation.
• To compare the predictive accuracy of different theoretical models against MD simulations and experimental data.
• To identify reasons for discrepancies and suggest future research directions.

Main Methods:

• Review and comparison of three theoretical models: Classical Nucleation Theory (CNT), Mean-Field Kinetic Nucleation Theory (MKNT), and Extended Modified Liquid Drop Model-Dynamical Nucleation Theory (EMLD-DNT).
• Analysis of existing experimental data for argon nucleation.
• Comparison of theoretical predictions with results from Molecular Dynamics (MD) simulations and Density Functional Theory (DFT) calculations.
• Evaluation of nucleation rates across different temperature-supersaturation domains.

Main Results:

• Nonclassical nucleation models (MKNT, EMLD-DNT) show good agreement (1-2 orders of magnitude) with MD simulations.
• Classical Nucleation Theory (CNT) deviates significantly (3-5 orders of magnitude) from MD simulations.
• DFT results align well with MKNT predictions (within one order of magnitude).
• All theoretical models exhibit substantial disagreement with experimental data, ranging from 4-8 orders of magnitude (MKNT) to up to 26 orders of magnitude (CNT).

Conclusions:

• Nonclassical nucleation theories and MD simulations provide a consistent picture of argon nucleation, distinct from CNT.
• A significant gap persists between theoretical/simulation predictions and experimental measurements of argon nucleation rates.
• Further research is needed, including experiments and simulations within a common temperature-supersaturation domain, to reconcile theoretical models with experimental observations and achieve a unified understanding of argon nucleation.