Speaker: Zhen Li, Assistant Professor of Mechanical Engineering, Clemson University
Title: Memory Effects in Coarse-Grained Modeling of Soft Matter
Abstract: Elimination of degrees of freedom from a complex dynamic system often introduces non-negligible memory effects, resulting in a non-Markovian, generalized Langevin equation (GLE) for the coarse-grained (CG) system in the context of the Mori-Zwanzig (MZ) formalism. For the conservation of momentum of the CG system, GLE can be reformulated into its pairwise version, i.e., non-Markovian dissipative particle dynamics (DPD) upon a pairwise decomposition. In this talk, I will introduce how to apply the rigorous theoretical approach of MZ to derive new governing equations for CG dynamics of polymer systems. I will demonstrate the coarse-graining procedure by running a molecular dynamics simulation of polymer melts and constructing the MZ-guided CG model directly from atomistic trajectories, as well as the computation of the memory kernel of dissipation in CG dynamics. Unlike ad hoc coarse-graining procedures, MZ-guided coarse-graining generates accurate and efficient CG model that reproduces the correct static and dynamic properties of its corresponding atomistic system. Moreover, I will introduce different coarse-graining strategies with GLE and non-Markovian DPD models to incorporate the memory effects in practical CG simulations.