Understanding dynamics in coarse-grained models. III. Roles of rotational motion and translation-rotation coupling in...

Area of Science:

• Computational chemistry
• Molecular dynamics
• Statistical mechanics

Background:

• Coarse-grained (CG) models simplify molecular systems but often omit rotational dynamics, leading to discrepancies with fine-grained (FG) simulations.
• Previous work established excess entropy scaling for translational motion in CG systems.

Purpose of the Study:

• To recover atomistic diffusion coefficients from CG dynamics by incorporating rotational motion.
• To investigate the universality of excess entropy scaling for both rotational and translational diffusion.
• To develop methods for estimating translation-rotation coupling in CG models.

Main Methods:

• Extraction of fine-grained (FG) rotational diffusion data.
• Integration of rotational dynamics into coarse-grained (CG) translational dynamics.
• Application of two methods for estimating translation-rotation coupling: rough hard sphere theory and rough Lennard-Jones model.

Main Results:

• A novel universality in excess entropy scaling between rotational and translational diffusion was identified.
• Successful recovery of FG diffusion coefficients from CG simulations by including rotational dynamics and translation-rotation coupling.
• Demonstrated that recapturing missing entropy is crucial for accurate FG diffusion prediction.

Conclusions:

• Incorporating rotational dynamics and translation-rotation coupling into CG models is essential for accurately predicting atomistic diffusion coefficients.
• Excess entropy scaling provides a universal framework for understanding diffusion in molecular fluids.
• This work bridges the gap between FG and CG dynamics, enhancing the predictive power of molecular simulations.