Research groups in the CMTC Members Hartmut Bracht , Physics (Ion Beam Induced Mixing, Atomic Mass and Heat Transport in Semiconductor Nanostructures) Nikos Doltsinis, Physics (Theory of functional Nano-structures) Harald Fuchs, Physics (Interface Physics) Svetlana Gurevich, Physics (Self-Organization and Complexity) Andreas Heuer, Chemistry (Dynamics and Phase Behaviour of Complex Systems as studied via Computer Simulations) Tilmann Kuhn, Physics (Nonequilibrium Dynamics in Semiconductors, Superconductors, and Ferromagnetic Films) Johannes Neugebauer, Chemistry (Theoretical Chemistry) Mario Ohlberger, Mathematics (Multiscale modeling and model order reduction for large-scale dynamic systems) Doris Reiter, Physics (Ultrafast Optics in Nanostructured Solids) Michael Rohlfing, Physics (Ab−Initio Approach to the Structure and to the Electronic and optical spectrum of low−dimensional systems) Uwe Thiele, Physics (Self-Organization and Complexity) Ernst-Ulrich Würthwein, Chemistry (Computational Chemistry) Associated Members Saeed Amirjalayer, group of Harald Fuchs, Physics, WWU Münster (Multiscale Simulation of porous and photoactive Systems) Vlad Cojocaru, MPI for Molecular Biomedicine Münster (Computational Structural Biology) Claudia Filippi, University of Twente, Enschede / The Netherlands (Electronic Structure Theory) Mark Waller, Shanghai University, China (Multiscale Modelling of Complex Molecular Systems) HARTMUT BRACHT - Physics, Materials Physics: Ion Beam Induced Mixing, Atomic Mass and Heat Transport in Semiconductor Nanostructures Ion beam mixing of isotopically modulated germanium multilayers: Classical molecular dynamics simulations of a self-atom cascade in germanium at 300 K and 1 picosecond after impact. The dark atoms have been displaced from their original lattice sites by more than the nearest-neighbour distance. A stable defect structure remains after the relaxation of the cascade. The consequence is a build-up of damage with continuous single ion implantations leading to the amorphization of the target material. This structural change affects physical properties such as heat transport capacity and melting point. These properties play an important role in the dynamics of cascade relaxation. Heat transport in isotopically controlled silicon nanostructures: Time-resolved relative lattice expansion of a Au/Cr layer deposited on natural Si (blue) and on a 20 bilayer structure of 30Si(10nm)/28Si(10nm) (red). The lattice expansion is measured in a pump-and-probe experiment (see insert) by means of X-ray diffraction after heating the metal layer with a laser pulse. The left axis displays the relative Au lattice expansion and the right axis the corresponding temperature ΔT=T-300 K. Solid lines represent best fits based on continuum theoretical simulations of the underlying heat transport problem. The cooling of the Au layer on the isotope structure is slower than the cooling of Au on natural Si. This reduction in the thermal conductivity of Si by isotopic modulation is qualitatively confirmed by molecular dynamics calculations. Engineering the isotope distribution is a striking concept to reduce the thermal conductivity of silicon without affecting its electronic properties. This concept can pave the way for future thermoelectric devices. top NIKOS DOLTSINIS - Physics, Solid-state Theory: Theory of functional Nano-structures Ab Initio Molecular Dynamics Theory of Functional Nanostructures Non−adiabatic Simulations of Photoinduced Processes simulation of rare events Calculation of free energy surfaces top HARALD FUCHS - Physics, Physics Institute: Interface physics (under construction) top UWE THIELE und SVETLANA GUREVICH - Physics, Theoretical Physics: Self-Organization and Complexity Basic mechanisms of self-organization; pattern formation in dynamic self-assembly systems; Analysis of complex systems and stochastic processes; Turbulent fields. Fig. 1: a. Turbulent temperature field in three-dimensional Rayleigh-Bénard convection, with hot resp. cold plumes emerging from the bottom and top boundaries; b. Resident times of inertial partilces in the wake of a cylinder; c. Estimates of the drift vector field (arrows) and the probability density function (color coded) of a synthetic time series of the noise-perturbed Haken-Zwanzig model together with an analytic approximation of the unstable manifold of the saddle point in the center (red curve); d. The pattern, produced during a Langmuir-Blodgett transfer onto a prestructured substrate. The occuring stripe pattern exhibits a 2:1 synchronization with the prestructure. top ANDREAS HEUER - Chemistry, Physical Chemistry: Dynamics and Phase Behaviour of Complex Systems as studied via Computer Simulations Mechanism of ion conduction in electrolytes (polymers, ionic liquids, inorganic systems) Linear and nonlinear transport as well as phase behavior of disordered systems Thermodynamic and phase behavior of DNA, protein, and membrane systems Structure formation on surfaces for deposition experiments top TILMANN KUHN - Physics, Solid-state Theory: Nonequilibrium Dynamics in Semiconductors, Superconductors, and Ferromagnetic Films The Kuhn group focuses their research on the theoretical description and simulation of the non-equilibrium dynamics in interacting many-particle systems. Examples for these are different solid state materials, nanostructures or ultra-cold atomic quantum gases. Results of two current sample projects are depicted in the graphics. Fig. 1: results of density matrix theory simulations of the influence of the electron-phonon interaction on the exciton population of a semi-conductor quantum dot after excitation with a frequency-modulated ("chirped") laser pulse. Fig. 2: structure of an array of two spin-torque nano-oscillators and the results of a micromagnetic simulation of the spin-wave expansion in the thin ferro-magnetic film connecting the oscillators. top JOHANNES NEUGEBAUER - Chemistry, Theoretical Chemistry: Theoretical Chemistry Subsystem and embedding approaches in (time-dependent) density-functional theory Wavefunction/DFT-embedding schemes Selective algorithms for theoretical vibrational, electronic, and vibronic spectroscopy Quantum chemical methods for photosynthetic systems Computational studies on structure, properties, and reactivity of organic compounds top MARIO OHLBERGER - Mathematics, Applied Mathematics: Multiscale modeling and model order reduction for large-scale dynamic systems Large-scale and multiscale dynamic systems arise in the modeling of many physical, chemical, biological, technical or environmental applications. Typical examples in electrochemistry are e.g. the underlying processes in fuel cells or batteries. Concerning multiscale modeling, we focus at deriving efficient numerical methods that are capable to describe meso- or macroscopic behavior of a system, while incorporating all essential features of the underlying processes on a much finer micro-scale. A further focus of our research is model order reduction for parameterized large-scale systems. Although the underlying systems might be very high dimensional or even infinite dimensional, it is usually observed that the parameter dependent solution trajectories form a compact and smooth low dimensional manifold and thus have an intrinsic structure for model order reduction. A typical approach is the so called reduced basis method, where a low dimensional linear approximation space is constructed with nearly optimal approximation properties with respect to the given solution manifold. Fig. 1: Detailed simulation of a Li-Ion battery model with the software framework DUNE on a 48mm x 24mm x 24mm computational domain with randomly generated electrode geometry. Coloring indicates Li^{+} concentration in active particles (electrolyte is not displayed). [Simulation by Stephan Rave within the BMBF-project MULTIBAT, No. 05M13PMA, Applied Mathematics Münster, 2014.] top DORIS REITER - Physics, Solid-state Theory: Ultrafast Optics in Nanostructured Solids We study dynamics on ultra-short time and length scales using theoretical models and numerical simulations. Our focus is on the light-matter interaction on the nano scale, where we consider semiconductor structures like quantum dots or metallic nano-structures showing plasmonic resonances. Our research topics are: Carrier dynamics in ultra-thin semiconductors Phonon influence on optically excited semiconductor quantum dots Interaction of nanostructures with complex light fields Controlling light using nanostructures top MICHAEL ROHLFING - Physics, Solid-state Theory: Ab−Initio Approach to the Structure and to the Electronic and optical spectrum of low−dimensional systems (under construction) top ERNST-ULRICH WÜRTHWEIN - Chemistry, Organic Chemistry - Experiment and Theory: Computational Chemistry Reaction mechanisms (intermediates, transition states) Unusual electronic structures (e.g. conducting polymers) Flexible organic molecules (flat potential energy surfaces) Theoretical treatment of spectroscopic properties (IR, NMR, UV) top Saeed Amirjalayer - Physics, Physics Institute (Associated Member): Multiscale Simulation of porous and photoactive Systems Atomistic Modelling of porous functional materials (Metal-Organic-Frameworks, Covalent-Organic Frameworks etc.) Structure determination with genetic algorithms Ab-initio parametrisation of force fields Quantum mechanical investigation of photoactive molecular machines top VLAD COJOCARU - MPI for Molekular Biomedicine (associated Member): Computational structural biology Structural basis for stem cell pluripotency Molecular simulations of protein/nucleic acids recognition Cooperative DNA recognition enabling combinatorial patterns of transcription regulation Transcription factor folding and its impact on DNA recognition Modeling and simulations of transcription factor/nucleosome recognition Classical atomistic molecular dynamics simulations Enhanced sampling simulations and free energy calculations Coarse grained and multi-scale molecular dynamics simulations top CLAUDIA FILIPPI - University of Twente, Enschede / The Netherlands (associated Member): Electronic Structure Theory Development of Quantum Monte Carlo Methods Multiscale Modelling of complex Systems (e.g. chromophores in proteins or molecules in solution) Development of CHAMP - Cornell-Holland Ab-initio Materials Package, a Quantum Monte Carlo suite of programs for electronic structure calculations of atoms, molecules, and solids Light-sensitive Proteins top MARK WALLER - Shanghai University / China, Theoretical Chemistry (associated Member): Multiscale Modelling of Complex Molecular Systems Adaptive-QM/MM approaches Non-local metaoptimization algorithms Distributed computing frameworks top