In this school, students will learn to conduct simulations in the fields of soft matter and porous materials using a combination of particle-based and lattice-based approaches. The main tool will be the simulation package ESPResSo (espressomd.org), an open-source particle-based simulation package focused on coarse-grained molecular dynamics models. In addition, it offers a wide range of schemes for solving electrostatics, magnetostatics, hydrodynamics, and electrokinetics, as well as algorithms for active matter and chemical reactions [1].

ESPResSo consists of an MPI-parallelized simulation core written in C++ and a scripting interface in Python, which integrates well with scientific and visualization Python packages such as numpy, scipy and pandas. ESPResSo relies on waLBerla, a high-performance lattice-Boltzmann library, for hydrodynamics and other lattice-based schemes for electrokinetics and related fields [2].

After an introduction to particle-based simulations, lattice-Boltzmann hydrodynamics, and the software interface, we will focus on the dynamics of soft matter and porous materials. Topics will include polymer dynamics, rheology studies using Lees-Edwards boundary conditions, dynamics of active bacteria, chemical reactions, multiphase and reactive flows as well as evaporation in porous environments. We will cover both particle-based approaches and continuum techniques such as the lattice-Boltzmann method for hydrodynamic interactions, as well as a diffusion-advection-reaction solver for modeling electrokinetics and reactive flows. The school will combine lectures on the underlying physics and simulation algorithms with hands-on sessions. The latter will mostly be conducted using ESPResSo, but will also include rapid prototyping of stencil methods for lattice-based modeling using waLBerla's code generation capabilities [3].

Many of the lectures and hands-on sessions will be taught by developers of ESPResSo. Hence, the school will also provide a platform for discussion between developers and users about the future of the software. Moreover, users can get advice on their specific simulation projects. Time will also be dedicated to research talks, which illustrate how the simulation software is applied and provide further background on the dynamics of soft matter and porous materials.

Scientific content

• Simulating Lennard-Jones systems
• Simulations of polymer dynamics including hydrodynamic interactions
• Studying systems under shear including particles and hydrodynamics interactions
• Simulation of self-propelled particles
• Simulating reactive flow and evaporation in porous geometries
• Numerical methods for two-phase fluid simulations
• Rapid prototyping of stencil methods
• Simulating chemical reactions by means of Monte Carlo methods