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Project B8 (N): Hydrodynamic Simulation of Passive and Active Janus Particles Janus particles are colloidal particles whose surface has been modified differently in different locations, creating so-called patches. The patches are designed in a way to generate directional interactions between the Janus particles. Janus particles, therefore, often self-assemble into ordered structures, commonly referred to as lattices or crystal structures, even though the system still is a colloidal solution. By variation of the chemical nature, size and location of the patches, a rich set of lattice structures is accessible. In our work so far, we have focused on triblock Janus particles, which carry attractive van-der-Waals patches on the poles and repulsive electrostatic charges around the equator. We developed a detailed dissipative-particle dynamics model for them, which includes surface chemistry and explicit solvent molecules. With this model and our newly devised adaptive metadynamics method, we could clarify their self-assembly into two-dimensional ordered […]

Project A10 (New): Population control of multiple walker simulations via a birth/death process Conventional Molecular Dynamics (MD) simulations are generally unable to access the long-timescale phenomena that are common in nature. This timescale problem comes from the fact that a typical free energy landscape consists of many metastable states separated by high free energy barriers. If the barriers are much higher than the thermal energy, the system is kinetically trapped in some metastable state and barrier crossings will be rare events on the time scales that we can simulate. One strategy to alleviate this time scale problem is to employ collective variable (CV) based enhanced sampling methods such as metadynamics. A common way to improve the performance of CV-based methods is to employ multiple walkers that share a bias potential and collaboratively sample the free energy landscape. In this way, one reduces the wall-clock time for convergence and makes better […]

Prof. Dr. Michael Vogel Institut für Festkörperphysik Technische Universität Darmstadt Hochschulstr. 6 D-64289 Darmstadt Tel: +49 6151 162933 Mail: michael.vogel@physik.tu-darmstadt.de Further information

Prof. Dr. Yongqi Wang Department of Mechanical Engineering Technische Universität Darmstadt Otto-Berndt-Str. 2 D-64287 Darmstadt Tel: +49 6151 1626202 Fax: +49 6151 1626203 Mail: wang@fdy.tu-darmstadt.de Further information

Prof. Dr. Florian Müller-Plathe Institut für Physikalische Chemie Technische Universität Darmstadt Alarich-Weiss-Str. 8 D-64287 Darmstadt Tel: +49 6151 16-22621 Fax: +49 6151 16-22619 Mail: f.mueller-plathe@theo.chemie.tu-darmstadt.de Further information

Prof. Dr.-Ing. Martin Oberlack Department of Mechanical Engineering Technische Universität Darmstadt Otto-Berndt-Str. 2 D-64287 Darmstadt Tel: +49 6151 1626200 Mail: oberlack@fdy.tu-darmstadt.de Further information

Prof. Dr. Omar Valsson Department of Chemistry University of North Texas 1155 Union Circle #305070 Denton, Texas 76203 Tel: +1 940 369 7593 Mail: omar.valsson@unt.edu Further information

Project C7: Dense active suspensions in the chaotic regime Active matter has become a quickly evolving field spanning from biology and physics to chemistry and engineering. Its defining property is the directed motion—translational, rotational, or both—of its constituents. This directed motion requires the steady input of free energy. Freed from the constraints of thermal equilibrium, active matter exhibits a wide range of novel phenomena; on the level of its single constituents up to emergent many-body collective and dynamic behavior. Extensively studied have been the aggregation of active particles into clusters, swarms, and other highly collective and dynamics states; but also spontaneous flow states where sufficiently high activity triggers the transition from a quiescent to a flowing fluid. At high densities, chaotic behavior has been reported in suspensions of bacteria and in numerical simulations. The aim of this project is to develop a comprehensive multiscale framework that bridges the properties of […]

Project A6: Coarse-grained models for dynamically asymmetric liquid mixtures under non-equilibrium conditions he main goal of this project is to gain better insight into the mapping of time-dependent properties of complex molecular systems, when studied using multiscale simulations. While the mapping of length scales is inherently defined by the coarse-graining procedure, the mapping of dynamic processes involves a complex combination of factors due to both the removal of degrees of freedom as well as approximations made in determining the coarse-grained (CG) interactions based on a reference all-atom (AA) model. As a consequence, the development of dynamically-consistent CG models is particularly challenging when various dynamic processes on different time scales coexist. To investigate these issues, we have focused on two important classes of systems, liquid crystals (LCs) and ionic liquids (ILs), which pair technological relevance with appropriate dynamics, and still show well defined modes of motion despite their significant complexity. In […]

Project A8: Roberto – Improved dynamics in hybrid particle-field molecular dynamics simulations of polymers We pursue one of the approaches to generate coarse-grained polymer models with correct dynamical properties. If such models can be made predictive for, say, polymer melt viscosities and other rheological characteristics they will make their important contribution toward, e.g., energy-efficient plastics processing or mechanical recycling of plastics waste. In funding period 2 (FP2), we have developed and implemented the Roberto method, a combination of hybrid-particle-field (hPF) molecular dynamics and slip-springs. The hPF method by itself is computationally fast, yet it allows coarse-grained or even atomistic accuracy for the base models. It performs excellent for static polymer properties, but provides a qualitatively wrong molecular mobility. As the field treatment of intermolecular interactions makes them effectively soft-core, atoms can superpose, and polymer chains can cut through one another. The artificial dynamics is remedied by the slip-springs, which restore […]