Thermodynamic curvature for attractive and repulsive intermolecular forces

Area of Science:

• Thermodynamics
• Statistical Mechanics
• Intermolecular Forces

Background:

• The Lennard-Jones potential is a fundamental model for describing interatomic and intermolecular interactions.
• Understanding the behavior of matter across different phases (vapor, liquid, solid) is crucial in physical chemistry.
• Thermodynamic curvature provides insights into the nature and strength of interactions within a system.

Purpose of the Study:

• To evaluate the thermodynamic curvature scalar R for the Lennard-Jones system across its phase space.
• To investigate the behavior of R along various phase equilibria, including vapor-liquid, liquid-solid, and vapor-solid.
• To analyze the relationship between R and the strength of attractive interactions.

Main Methods:

• Calculation of the thermodynamic curvature scalar R in phase space for the Lennard-Jones system.
• Analysis of R along lines of vapor-liquid, liquid-solid, and vapor-solid equilibria.
• Application of the Weeks-Chandler-Anderson perturbation ansatz to study the dependence of R on interaction strength.

Main Results:

• The thermodynamic curvature scalar R was evaluated across vapor, liquid, and solid phases.
• The line R=0 was identified, separating regions of attractive (R<0) and repulsive (R>0) interactions.
• A clear transition from repulsive (R>0) to attractive (R<0) interactions was observed as attraction was introduced into the intermolecular potential.

Conclusions:

• The thermodynamic curvature scalar R effectively quantifies interaction strength in the Lennard-Jones system.
• The study delineates phase space regions based on interaction type (attractive vs. repulsive).
• The findings demonstrate how modifying intermolecular potentials influences interaction characteristics.