Dynamical simulation of dipolar Janus colloids: equilibrium structure and thermodynamics

Area of Science:

• Colloid science
• Statistical mechanics
• Computational physics

Background:

• Dipolar Janus (DJ) particles possess distinct hemispheric charge interactions.
• Understanding their microstructures and thermodynamics is crucial for materials science.
• Previous models often used discontinuous potentials, limiting simulation methods.

Purpose of the Study:

• To investigate the static microstructures and thermodynamics of DJ particles.
• To compare a detailed pointwise (PW) model with a coarse-grained (CG) model.
• To explore the structural behavior of DJ particles in liquid phases.

Main Methods:

• Molecular dynamics simulations using continuous potentials for pairwise interactions.
• Modeling DJ particles with soft repulsion and orientation-dependent electrostatics.
• Utilizing a rigorous pointwise (PW) model and its isotropic coarse-graining (CG) limit.

Main Results:

• The CG model accurately predicts equilibrium structure and ensemble free energy compared to the PW model.
• Simulations showed reversible structures without long-range correlations within studied parameters.
• Time-dependent simulations indicated no chain structure formation in liquid phases for DJ particles.

Conclusions:

• Continuous potentials enable conventional molecular dynamics simulations for DJ particles.
• The CG model provides a reliable approximation for the PW model under specific conditions.
• DJ particles exhibit distinct liquid-phase behavior compared to simple polar fluids, lacking chain formation.