On the Density Dependence of the Integral Equation Coarse-Graining Effective Potential

Area of Science:

• Computational Physics
• Polymer Science
• Statistical Mechanics

Background:

• Coarse-graining (CG) methods accelerate simulations of large-scale systems.
• Bottom-up CG approaches require accurate effective interactions from atomistic data.
• Preserving structural and thermodynamic properties is crucial for reliable CG.

Purpose of the Study:

• To detail the integral equation coarse-graining (IECG) method, incorporating density as an active variable.
• To validate the IECG method by comparing its results with atomistic simulations for polymer melts.
• To analyze the influence of repulsive and attractive interactions on structural and thermodynamic properties in CG simulations.

Main Methods:

• Developed and applied the integral equation coarse-graining (IECG) method.
• Treated system density as an intrinsic and active variable within the IECG framework.
• Performed extensive simulations of polymer melts and compared results with atomistic simulations.

Main Results:

• IECG simulations showed excellent agreement with atomistic simulations for structural properties (pair-correlation functions, form factors).
• Both methods accurately predicted thermodynamic properties like pressure.
• Short-range repulsive CG interactions primarily determined polymer liquid structure, while long-range attractive interactions were essential for accurate pressure prediction.

Conclusions:

• The IECG method, with density as an active variable, provides a reliable and computationally efficient approach for modeling polymer melts.
• The findings highlight the distinct roles of repulsive and attractive forces in determining the structural and thermodynamic behavior of polymeric liquids.
• This work supports the foundational principles of liquid state theory regarding potential influences on phase diagrams.