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2018 – Publications

Dr. Kostas Daoulas Max Planck-Institut für Polymerforschung Ackermannweg 10 D-55128 Mainz Tel: +49 6131 379 218 Fax: :+49 6131 379340 Mail: kostas.daoulas@mpip-mainz.mpg.de Further information

Project C4 (Completed): Coarse-graining frequency-dependent phenomena and memory in colloidal systems Electrostatic interactions can strongly influence the behavior of macromolecular systems. A particular challenge for their prediction is the accurate, albeit computationally tractable, handling of the influence of water dipoles on the potentials. To address this challenge, we develop an efficient and accurate numerical framework for nonlocal electrostatics of large molecular systems. An improved understanding of the influence of water structure on electrostatics has far-reaching applications: the results of the project can, in principle, be used wherever implicit water models are desired, but where a simple structureless continuum is insufficiently accurate. This project has ended in June 2018.

Project C6 (Completed): Linking hydrodynamics and microscopic models of wet active matter with anisotropic particles The goal of this project is to develop a systematic, quantitative coarse-graining approach for a class of inherently non-equilibrium systems, namely suspensions of self-propelled particles. We link particle based models with effective hydrodynamic models within a multiscale framework based on sequential coupling and parameter passing. To this end, we combine microscopic Stokesian dynamics simulations with a mesoscopic kinetic model coupled to the macroscopic Stokes equation, and, in a second step, derive an effective hydrodynamic description in terms of particle density, polarization and nematic order parameter profiles. The multiscale scheme is applied to systems of self-propelled rod-like magnetic colloids suspended in a fluid. This is motivated by recent experiments on magnetotactic bacteria, which have shown that the interplay of internal drive (self-propulsion, mutual interactions) and external drive (magnetic field, oxygen gradient) in these systems leads to […]

Project G: Central soft matter simulation platform The goals of project G in the second funding phase of the TRR 146 have been the implementation of new methods of general interest into the molecular dynamics simulation environment ESPResSo++ Guzman et al. (2019), which can be used as foundation for research projects inside the TRR 146, and the optimization of ESPResSo++ to efficiently use modern HPC resources and therefore to become performance competitive with state-of-the-art MD environments like LAMMPS. Project G has been successful integrating new simulation methods by coupling ESPResSo++ with the ScaFaCos library Hofmann et al. (2018), Arnold et al. (2013) to provide fast parallelized long-range interaction algorithm (e.g. P3M / multipolar P3M), developing and implementing a new approach for Lees-Edwards boundary conditions to provide a fast parallel implementation of shear boundary conditions. The performance optimization of the ESPResSo++ environment included to change the memory layout to benefit from […]

Project B6: Topological validation of coarse-grained polymer models Computational studies of polymer-based materials on large length and time scales require mesoscopic models: drastically coarse-grained descriptions where non-bonded potentials between interacting particles are on the order of the thermal energy. Such “soft” models are either used as “stand alone” descriptions or as elements of strategies, where the microscopic description of the material is recovered through sequential backmapping in a hierarchy of mesoscopic models. In the previous funding period, we focused on using single-chain topology ─ polymer knots ─ to validate mesoscopic models and hierarchical backmapping schemes for bulk high-molecular-weight polymer melts. We made three important findings: A) We demonstrated that polymer knots are, in general, multiscale objects, i.e. they simultaneously depend on microscopic and medium-scale features. As such, they cannot be always accurately described by mesoscopic models. B) Nevertheless, we identified conditions when mesoscopic models can quantitatively reproduce knotting properties of […]

Project A5 (Completed): Heat transfer in polymer nanocomposites A multiscale approach to heat transfer in soft matter will be developed. In particular, coarse-grained models of polymer nanocomposites including graphite flakes will be built and employed to obtain and characterize relaxed structures of such materials. Atomistic details will be reinserted in these structures and heat transfer will be characterized at this level of description to obtain reference data. Then, the question will be addressed how the coarse-grained models have to be modified in order to characterize heat transport in the nanocomposites directly at the coarsened level of description. This project has ended in June 2018.

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