Particle-based material description

Force fields as used in Molecular Dynamics simulations describe the potential energy of a molecular system, either in atomistic or coarse-grained resolution. Their functional form and parameters are identified in either physical or chemical experiments or quantum mechanical calculations. Therefore, they are able to accurately model the molecular structure of the described material and thus can be used to investigate effects on the molecular level.

From a computational point of view, the number of degrees of freedom to be handled in particle systems at atomistic resolution prohibits the computation of many complex materials. However, coarse graining allows for a significant reduction of the degrees of freedom in various particle applications with sufficient accuracy. This is achieved by subsuming a certain number of atoms into a so-called superatom (cf. Fig. 1).

As sample systems, we currently use a coarse-grained description for polystyrene [1] as well as a generic coarse-grained model [2]. Currently, we are examining the effect of considering interaction potentials capable of bond breakage (see also Fracture of polymers), for instance Morse potentials [3].

–Dr.-Ing. Maximilian Ries and Felix Weber (M. Sc.)

Fig. 1: Polystyrene chain in atomistic (a) and coarse-grained (b) resolution.

[1] H.-J. Qian, P. Carbone, X. Chen, H. A. Karimi-Varzaneh, C. C. Liew, and F. Müller-Plathe, “Temperature-Transferable Coarse-Grained Potentials for Ethylbenzene, Polystyrene, and Their Mixtures”, Macromolecules, vol. 41, pp. 9919-9929, 2008

[2] M. Ries, J. Seibert, P. Steinmann, S. Pfaller, “Applying a generic and fast coarse-grained molecular dynamics model to extensively study the mechanical behavior of polymer nanocomposites”, eXPRESS Polymer Letters, vol. 16, pp. 1304-1321, 2022

[3] P. M. Morse, “Diatomic Molecules According to the Wave Mechanics. II. Vibrational Levels”, Physical Review, vol. 34, pp. 57-64, 1929