Simulations of dipolar fluids using effective many-body isotropic interactions

Area of Science:

• Statistical Mechanics
• Computational Physics
• Physical Chemistry

Background:

• Pairwise-additive anisotropic dipole-dipole interactions can be represented by many-body isotropic interactions.
• Effective many-body interactions include n-body contributions, with leading terms being -r(-6) attraction and Axilrod-Teller interaction.

Purpose of the Study:

• To compare a fluid with leading two-body and three-body interactions to an equivalent dipolar soft-sphere fluid.
• To determine conditions where effective many-body interactions reproduce dipolar fluid structures using molecular simulations.
• To investigate the impact of Axilrod-Teller interaction strength on vapor-liquid phase diagrams.

Main Methods:

• Molecular simulations were employed to analyze fluid-phase structures.
• Comparison between effective many-body interactions and dipolar soft-sphere fluid.
• Determination of vapor-liquid phase diagrams for varying Axilrod-Teller contributions.

Main Results:

• Effective many-body interactions accurately model dipolar fluid structures at moderately high temperatures.
• The model fails at low temperatures due to particle chaining, but adjustments to interaction coefficients improve accuracy.
• Increased Axilrod-Teller interaction strength reduces critical temperature and density, eventually suppressing condensation.

Conclusions:

• Effective many-body interactions, particularly with adjusted Axilrod-Teller terms, can effectively describe dipolar fluid structures across various temperatures.
• Particle chaining at low temperatures can be managed by modifying interaction coefficients.
• The strength of the three-body Axilrod-Teller interaction significantly influences phase behavior, including critical properties and the condensation transition.