Comparing zero-parameter theories for the WCA and harmonic-repulsive melting lines

Area of Science:

• Thermodynamics
• Statistical Mechanics
• Computational Physics

Background:

• The melting line of the Weeks-Chandler-Andersen (WCA) system is crucial for understanding phase transitions.
• Previous studies compared WCA melting line predictions with analytical hard-sphere approximations.
• Isomorph theory offers a novel approach for predicting thermodynamic properties based on a single reference state.

Purpose of the Study:

• To investigate the predictive power of isomorph theory for the WCA system's melting line.
• To compare isomorph theory predictions with hard-sphere approximations across different temperature regimes.
• To analyze the role of harmonic-repulsive potentials and uncorrelated pair collisions in isomorph theory.

Main Methods:

• Utilized isomorph theory with a harmonic-repulsive potential approximation for the WCA potential.
• Assessed the assumption of uncorrelated pair collisions within the isomorph theory framework.
• Determined the face-centered-crystal to fluid coexistence line for harmonic-repulsive particles.

Main Results:

• Isomorph theory provides excellent predictions for the WCA melting line at high temperatures.
• Hard-sphere theory-based predictions show better accuracy at lower temperatures.
• The accuracy of isomorph theory at high temperatures may stem from a cancellation of errors.

Conclusions:

• Isomorph theory presents a promising zero-parameter approach for predicting melting lines in soft-matter systems.
• The study highlights the temperature-dependent performance of different theoretical models.
• Further investigation into error cancellation mechanisms in isomorph theory is warranted.