Berlin 2024 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 2: Modeling and Simulation of Soft Matter I

CPP 2.6: Talk

Monday, March 18, 2024, 11:00–11:15, H 0107

Transferable Local Density-Dependent Friction in tert-Butanol/Water Mixtures — •Moritz Mathes, Viktor Klippenstein, and Nico van der Vegt — TU Darmstadt, Germany

Coarse-grained (CG) models in molecular dynamics (MD) simulations allow to represent the structure of an underlying all-atom (AA) model by deriving an effective interaction potential. However, this leads to a speed-up in dynamics due to the lost friction, which is especially pronounced in CG implicit solvent models. Adding a thermostat based on the Langevin equation (LE) allows to represent the long-time dynamics of CG particles by reintroducing friction to the system. To improve the representability in CG models of heterogenous molecular mixtures and their transferability over the mixture compositions, we parametrise a LE thermostat, where the friction coefficient depends on the local particle density (LD). We simulated tert-butanol/water mixtures over a range of compositions, which show distinct clustering behaviour. For these systems we parametrised three different CG models with: 1. no thermostat friction (CG-MD), 2. fixed friction (CG-LE), and 3. local density-dependent friction (CG-LD). The thermostat friction was iteratively optimised with a Markovian variant of the recently introduced Iterative Optimization of Memory Kernels (IOMK) method [1]. We find that the CG-LD model reproduces the AA diffusion coefficients well over the full range of mixtures and is therefore transferable. In addition, I will discuss the role of conservative interactions on dynamics and remaining representability challenges beyond diffusion.

[1] J. Chem. Theory Comput. 2023, 19, 1099-1110

Keywords: coarse-graining; Langevin equation; implicit solvent; local particle density; molecular dynamics simulations