Loss of Molecular Roughness upon Coarse-Graining Predicts the Artificially Accelerated Mobility of Coarse-Grained Molecular Simulation Models

Abstract

Coarse-grained models include only the most important degrees of freedom to match certain target properties and thus reduce the computational costs. The dynamics of these models is usually accelerated compared to those of the parent atomistic models. We propose a new approach to predict this acceleration on the basis of the loss of geometric information upon coarse-graining. To this end, the molecular roughness difference is calculated by a numerical comparison of the molecular surfaces of both the atomistic and the coarse-grained systems. Seven homogeneous hydrocarbon liquids are coarse-grained using the structure-based iterative Boltzmann inversion. An acceleration factor is calculated as the ratio of diffusion coefficients of the coarse-grained and atomistic simulation. The molecular roughness difference and the acceleration factor of the seven test systems reach a very good linear correlation.

Swarm-CG: Automatic Parametrization of Bonded Termsin Coarse-Grained Models of Simple to Complex Molecules via Fuzzy Self-Tuning Particle Swarm Optimization

“…Notably, the average and spread of Rg values obtained for the optimized CG model are just slightly larger respect to those of the AA-mapped reference trajectory (Figure 4b: ΔRg of 0.7 Å). Although the error is substantially negligible, this is consistent with the higher dynamicity of CG models compared to the AA ones 82 (this is more evident in BTT, as this motif allows stronger core-to-arms and arms-to-arms interactions compared to e.g. BTA).…”

A Coarse-Grained Force Field for Silica–Polybutadiene Interfaces and Nanocomposites

“…The dynamical properties of the melt in contact with the coarse-grained silica models have also been tested and are generally consistent with the reference atomistic results, but with a margin of error. This is not surprising, as any coarse-graining procedure involves a loss of some chemical detail, and this tends to have a larger impact on the dynamical properties than on the structural ones [ 56 , 57 , 58 ].…”

“…Such an approximation is reasonable for hydrocarbons, as they are prototypical apolar compounds. In addition, the potential energy surfaces describing intra- and inter-molecular interactions tend to be smoother for CG model, and this results in faster dynamics in comparison with AA ones [ 56 , 57 , 58 ].…”

Grain Shape Dynamics for Molecular Simulations at the Mesoscale

“…The interactions between the coarse grains are therefore usually soft, [17] which results in a poor compressibility prediction, [18] topological violations caused by chain crossings, [19] and unrealistic flow. [20] By explicitly taking into account the shape of the grain with an anisotropic model, these artifacts can be reduced, [21] because the resulting interactions will be less soft and the elongated grains fill the gap between consecutive grains in stretched chain segments. We therefore expect that the dynamical shape of grains will improve the quality of the polymer model.…”