Condensation vs cavitation in water: A simulation study

Area of Science:

• Thermodynamics
• Physical Chemistry
• Atmospheric Science

Background:

• Condensation and cavitation are critical phenomena in various scientific and industrial applications.
• Understanding nucleation mechanisms in water is essential for predicting its behavior in different environments.

Purpose of the Study:

• To investigate and compare condensation and cavitation nucleation in water using molecular dynamics simulations.
• To determine interfacial free energies across a range of supersaturation using multiple simulation methods.
• To validate Classical Nucleation Theory for small nuclei and explore temperature-dependent differences in nucleation behavior.

Main Methods:

• Molecular dynamics simulations were employed to study water nucleation at 450 K and 550 K.
• Interfacial free energies were calculated using direct coexistence, seeding, and spontaneous nucleation simulations.
• Cavitation data was incorporated from a previous study for comparative analysis.

Main Results:

• Classical Nucleation Theory is valid even for nuclei as small as two molecular diameters.
• Condensation rates increase significantly with temperature due to lower interfacial free energy.
• Interfacial free energy trends differ between condensation (nearly constant to slightly increasing) and cavitation (decreasing) with nucleus size.

Conclusions:

• Water nucleation mechanisms, specifically condensation and cavitation, are distinct and temperature-dependent.
• Interfacial free energy and kinetic pre-factors play crucial roles in governing nucleation rates.
• Molecular structure at the interface shows temperature and curvature dependence, but no direct link to interfacial free energy was found.