Phase behavior of density-dependent pair potentials.

Area of Science:

• Thermodynamics
• Materials Science
• Statistical Mechanics

Background:

• Phase diagrams are crucial for understanding material behavior.
• Traditional models often assume density-independent interparticle potentials.
• Complex fluids and molecular liquids exhibit intricate phase behaviors.

Purpose of the Study:

• To calculate phase diagrams using advanced thermodynamic perturbation theories.
• To investigate the impact of density-dependent interparticle potentials on phase transitions.
• To identify novel phase transitions and triple points.

Main Methods:

• Utilizing third-order thermodynamic perturbation theory (TPT) for fluid phases.
• Employing first-order TPT for solid phases.
• Modeling interparticle potentials with hard sphere repulsion and density-dependent attractive tails (inverse power law or Yukawa).

Main Results:

• Discovered novel phase transitions beyond those from density-independent potentials.
• Observed isostructural solid-solid and liquid-liquid transitions.
• Identified new stable and metastable triple points, including fluid-fcc-fcc and liquid-liquid-fcc configurations.

Conclusions:

• The density dependence of interparticle potentials significantly influences phase diagrams.
• Novel phase transitions and triple points arise from density-varying potentials.
• Some predicted transitions require experimental verification in complex and molecular liquids.