Extension of classical nucleation theory for uniformly sheared systems

Area of Science:

• Physical Chemistry
• Materials Science
• Non-equilibrium Thermodynamics

Background:

• Nucleation is a critical out-of-equilibrium process significantly influenced by external fields.
• Classical nucleation theory (CNT) provides a foundational framework but often requires extensions for complex conditions.
• Understanding shear flow effects is crucial for materials processing and phenomena involving fluid dynamics.

Purpose of the Study:

• To extend classical nucleation theory (CNT) for systems under homogeneous shear flow.
• To introduce a shear-rate-dependent effective temperature and account for nucleus formation anisotropy.
• To analyze molecular dynamics simulation results across various shear rates and undercoolings using the extended theory.

Main Methods:

• Developed a simple extension of classical nucleation theory (CNT).
• Incorporated anisotropy of critical nucleus formation.
• Introduced a shear-rate-dependent effective temperature.
• Performed extensive molecular dynamics simulations.

Main Results:

• Observed a maximum in the nucleation rate at a specific shear rate where system relaxation time is comparable to the inverse shear rate.
• The extended theory accurately analyzes simulation data over a broad range of shear rates and undercoolings.
• Demonstrated that shear effects primarily modify the kinetic prefactor and effective temperature, not the thermodynamic description.

Conclusions:

• The proposed extension of CNT effectively describes nucleation under shear flow.
• Shear flow introduces a non-monotonic dependence of nucleation rate on shear rate.
• This work provides a refined theoretical framework for nucleation in flowing systems without altering the fundamental thermodynamic principles.