Homogeneous SPC/E water nucleation in large molecular dynamics simulations

Area of Science:

• Physical Chemistry
• Computational Physics
• Materials Science

Background:

• Accurate measurement of nucleation rates is crucial for understanding phase transitions.
• Discrepancies exist between experimental and theoretical nucleation rates, particularly for water.
• Previous simulations were limited by system size, hindering accurate rate determination.

Purpose of the Study:

• To perform direct, large-scale molecular dynamics simulations of homogeneous water nucleation.
• To accurately measure extremely low nucleation rates and associated cluster properties.
• To compare simulation results with existing nucleation theories and models.

Main Methods:

• Direct large molecular dynamics simulations using up to ~4x10^6 SPC/E water molecules.
• Implementation of a new functional form for the Yasuoka-Matsumoto nucleation rate measurement technique (threshold method).
• Precise measurement of size distributions, sticking efficiencies, cluster temperatures, and internal densities.

Main Results:

• Accurate nucleation rates measured down to ~10^19 cm^-3 s^-1, bridging the gap with experimental rates (~10^17 cm^-3 s^-1).
• Classical nucleation theory overestimates rates, while semi-phenomenological models show better agreement.
• Post-critical clusters exhibit bulk-like temperatures and slightly higher densities (~5%).

Conclusions:

• Large-scale simulations provide accurate nucleation rates and detailed cluster properties.
• Classical nucleation theory requires significant refinement for water.
• A re-calibrated Hale-type scaling relation shows remarkable consistency across a wide range of conditions.