Direct calculation of the critical Casimir force in a binary fluid

Area of Science:

• Physics
• Soft Matter Physics
• Computational Physics

Background:

• Critical Casimir effects are quantum-vacuum fluctuations influencing macroscopic objects near critical points.
• Understanding these effects is crucial for nanotechnology and materials science.
• Direct simulation of binary fluid demixing offers a novel approach to studying these phenomena.

Purpose of the Study:

• To directly simulate and investigate critical Casimir effects in a model binary fluid undergoing a demixing transition.
• To analyze the behavior of generalized pressure and its components in slab geometry.
• To explore the pressure anisotropy and its relation to universal scaling functions.

Main Methods:

• Utilizing direct simulation of a model binary fluid.
• Employing the semi-grand-canonical ensemble in a slab geometry.
• Analyzing the excess generalized pressure (P⊥ - nμ) to quantify Casimir forces.

Main Results:

• Successfully accessed critical Casimir effects through direct simulation.
• Observed that excesses of perpendicular pressure (P⊥) and nμ are individually larger than the Casimir force.
• Identified a critical pressure anisotropy between forces parallel and perpendicular to confinement.
• Demonstrated that this anisotropy collapses onto a universal scaling function.

Conclusions:

• Direct simulation is a viable method for studying critical Casimir effects in binary fluid systems.
• The observed pressure anisotropy and its universal scaling provide new insights into critical phenomena.
• This work bridges theoretical predictions and computational evidence for critical Casimir forces.