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Scientific computing on super-computers has become one of the standard methods of research in physics. This is clearly demonstrated by the articles in this section, which present a selection of projects related to physical re-search currently running at the HLRS. The presented work does not only cover a wide range of physics, it is also dominated by long-term projects which continuously have progressed...
We investigate the chain conformations and phase separation in binary polymer blends. Using large scale semi-grandcanonical Monte Carlo simulations and finite size scaling, we investigate the molecular extension and the intermolecular paircorrelation function in thin films with hard, non-preferentially adsorbing surfaces. The interplay between chain conformations, demixing and the validity of mean...
Lattice Monte-Carlo simulations of quantum chromodyanmics (QCD) have shown that strongly interacting matter undergoes a phase transition at some temperature Tc [1]. Above the transition temperatures Tc hadrons (the experimentally observed strongly interacting particles) cease to exist and a new state of matter, the so-called quark-gluon plasma (QGP) was predicted to exist [1]...
Simulating the flow of suspensions is an extremely difficult and demanding problem. Suspensions are mixtures of fluid and granular materials, and each component alone is a challenge to numerical modelers. When they are combined in a suspension, neither component can be neglected, so all the difficulties of both fluids and grains must be solved, in addition to the new problem of describing the interaction...
In the current project, we simulate thermal convection and generation of magnetic fields inside a fully convective star, like an M-dwarf or a T-tauri star. The numerical resolution required to reasonably well describe convection properties inside the star is 2563 to 5123.
Symbiotic systems consist of a red giant undergoing strong mass loss and a white dwarf. More than hundred symbiotic stars are known, but only about ten systems show jet emission. The most famous systems are R Aquarii, CH Cyg and MWC 560. While the first two objects are seen at high inclinations — a fact which makes it possible to study the morphology and structure of jets of symbiotic stars — the...
We discuss image potential states on an insulator surface, LiF(001)-(1×1), within ab-initio many-body perturbation theory. The image potential states originate from the interaction of electrons outside the surface with polarization charges inside the substrate. They are responsible for characteristic features in the electron energy loss spectrum of the material. The onset of excitation energies is...
We have used the vectorised and parallelised magnetohydrodynamics code NIRVANA on the NEC SX-5 and the new SX-6 installation in parallel mode to simulate the interaction of jets with a galactic wind that might be typical for the star-bursting radio-galaxies of the early universe.
In the following we give a summary of the computational physics articles presented in the frame of solid-state physics. In the project of Prof. P. Nielaba from the physics department in Konstanz new insights into the electronic transport in nano-wires, elastic constants of model colloids, pore condensates and phase transitions in nano-systems in ex-ternal potentials and reduced geometry have been...
Elastic and structural properties of model colloids have been studied with particular emphasis on the effect of quenched impurities and of external fields. The structural and electronic properties of atomic wires has been analysed. In the following sections an overview is given on the results of our recent computations on quantum effects, structures and phase transitions in such systems.
Resolving the atomic and electronic structures of nanoclusters represents an important preliminary for their controlled use in future nanotechnologies. Here we show through the comparison of density-functional calculations with high-resolution photoelectron spectroscopy that 1.4 nm nanoparticles of silver (negatively charged clusters of 53 to 58 atoms) are icosahedral-based structures displaying a...
Large scale molecular dynamics (MD) computer simulations are used to study the amorphous alkali silicates (Li2O)(2·SiO2) [LS2], (K2O)(2·SiO2) [KS2], and (0.5·Li2O)(0.5·K2O)(2·SiO2) [LKS2]. These systems are characterized by a fast alkali ion motion in a relatively immobile Si-0 matrix. We investigate the so-called mixed alkali effect (MAE) which is reflected as a significant decrease of the alkali...
The adsorption on methylchloride (CH3Cl) on the Si(001) surface is studied by first-principles calculations using the gradient-corrected density-functional theory (DFT-GGA) together with ultrasoft pseudopotentials and a plane-wave basis set. The energetically favoured adsorption geometries are examined with respect to their bandstructures, surface dipoles and charge transfer characteristics.
Quantum Monte Carlo simulations are used to study the dynamics and the critical properties of strongly correlated systems relevant to the fields of cold quantum gasses and high-Tc superconductivity. Recent advances in cooling techniques of quantum gasses allow to reach the degenerate regime for fermionic samples. Loading these systems on optical lattices can bring the gas to a strongly...
We present a numerical study of the doping dependence of the spectral function of the n-type cuprates. Using cluster-perturbation theory and the self-energy-functional approach, we calculate the spectral function of the Hubbard model with next-nearest neighbor electronic hopping amplitude t′ = −0.35t and on-site interaction U = 8t at half filling and doping levels ranging from x = 0.077 to x = 0.20...
Numerical simulation of complex flows has always demanded the biggest com-puters both in storage capacity and in performance that were available on the market. This situation is still going on. The following paragraph repre-sents a selection of papers that were submitted as yearly demanded progress reports to the HLRS. Although most of the reports revealed a very high sci-entific standard those papers...
Investigations on laminar-turbulent transition for high-speed flows at hypersonic Mach-numbers will be presented. Dissociation takes place above a temperature of T>2000K within the boundary layer, a temperature which is reached easily at Mach-numbers above M=5. Additional degrees of freedom for the energy must be taken into account by employing a vibrational energy equation. Chemical reactions...
By means of spatial direct numerical simulations (DNS) based on the complete Navier-Stokes equations the effect of three-dimensional discrete suction on the spatial development of a laminar boundary-layer flow generic for the front part of a swept-back airliner wing has been investigated. The baseflow is an accelerated Falkner-Skan-Cooke boundary layer, on a swept wedge with semi-opening angle of...
Shock-wave/turbulent-boundary-layer interaction compression-ramp flow is a canonical test configuration for statistical turbulence modeling. Extensive experimental data are available, whereas computational data focus mainly on Reynolds-averaged computations employing a wide range of turbulence models. In figure 1 basic flow features are sketched [Zhe91]. The undisturbed incoming turbulent boundary...
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