Metastable Lennard-Jones fluids. II. Thermal conductivity

Area of Science:

• Thermodynamics and Statistical Mechanics
• Computational Physics
• Fluid Dynamics

Background:

• Understanding thermal transport properties is crucial for characterizing fluid behavior.
• Metastable fluid states (superheated liquids, supercooled liquids, supersaturated vapor) present unique challenges for property calculations.
• The Lennard-Jones fluid model serves as a fundamental system for studying phase transitions and transport phenomena.

Purpose of the Study:

• To compute the thermal conductivity (λ) of a Lennard-Jones fluid across stable and metastable regions.
• To investigate the relationship between thermal conductivity and thermodynamic variables (temperature, density, pressure).
• To explore the behavior of excess thermal conductivity near the liquid-gas phase transition and its connection to the spinodal.

Main Methods:

• Employed equilibrium molecular dynamics simulations.
• Utilized the Green-Kubo formalism for thermal conductivity calculation.
• Covered a wide range of reduced temperatures (0.4–2.0) and densities (0.01–1.2), including 130 metastable states.

Main Results:

• Developed equations describing the regular part of thermal conductivity's dependence on temperature, density, and pressure.
• Identified that lines of constant excess thermal conductivity (Δλ) form an envelope coinciding with the spinodal curve in (p, T) space.
• Observed that gradients of excess thermal conductivity approach infinity as the spinodal is approached for superheated liquids and supersaturated vapors.

Conclusions:

• The spinodal curve acts as an envelope for lines of constant excess thermal conductivity in the liquid-gas phase transition region.
• The study provides a detailed characterization of thermal conductivity in both stable and metastable fluid states.
• Findings offer insights into the behavior of thermal transport properties near critical phenomena and phase boundaries.