A simulation method for the phase diagram of complex fluid mixtures.

Area of Science:

• Physical Chemistry
• Computational Fluid Dynamics
• Materials Science

Background:

• Determining phase diagrams of complex fluid mixtures via computer simulations presents significant challenges.
• Traditional methods like Gibbs ensemble simulations struggle with efficient molecule transfer for complex fluids, such as polymers.
• Simulating coexisting phases in a single cell is complicated by a moving interface, hindering concentration profile analysis.

Purpose of the Study:

• To develop a new, more efficient computational method for calculating phase diagrams of complex fluid mixtures.
• To address the limitations of existing simulation techniques in accurately predicting phase behavior.

Main Methods:

• A novel single-cell simulation approach is proposed, utilizing a spatial concentration autocorrelation function.
• This function spatially aligns instantaneous concentration profiles across simulation snapshots.
• The aligned profiles enable the calculation of average concentration profiles and coexisting concentrations.

Main Results:

• The method was successfully applied to calculate phase diagrams for the Widom-Rowlinson model and polymer blends.
• Results showed excellent agreement with established methods, except near the critical point due to interface broadening and finite-size effects.
• The proposed technique demonstrates robustness for complex fluid mixtures.

Conclusions:

• The new single-cell simulation method provides an effective way to determine phase diagrams for complex fluids.
• It offers a simpler and more accessible alternative to existing computational approaches.
• The method is broadly applicable to various complex fluid mixtures.