Failure of the constrained equilibrium hypothesis in nucleation

Area of Science:

• Physical Chemistry
• Computational Physics
• Materials Science

Background:

• Nucleation theory describes the initial stage of phase transitions, such as freezing.
• The Becker-Doring-Tunitskii model provides a theoretical framework for nucleation.
• Molecular dynamics (MD) simulations offer atomistic insights into freezing processes.

Purpose of the Study:

• To evaluate the accuracy of the Becker-Doring-Tunitskii model in simulating freezing.
• To assess the validity of the constrained equilibrium hypothesis (CEH) in nucleation theory.
• To investigate methods for determining critical nucleus size during phase transitions.

Main Methods:

• Solving the Becker-Doring-Tunitskii coupled differential equations.
• Comparing theoretical predictions with results from molecular dynamics (MD) simulations of freezing.
• Examining criteria for identifying critical nucleus size.

Main Results:

• MD simulation results for freezing could not be reproduced by the Becker-Doring-Tunitskii model without violating the CEH.
• A physically plausible explanation for the violation of the CEH was proposed.
• A new criterion for critical nucleus size, which incorporates the CEH, was found to be potentially inaccurate.

Conclusions:

• The constrained equilibrium hypothesis (CEH) may not be universally applicable in nucleation phenomena.
• Deviations from CEH are necessary to align theoretical models with MD simulation data for freezing.
• Alternative methods for determining critical nucleus size, avoiding CEH, warrant further investigation.