Group seminar Theoretical Physics III

23.10.2019 10:45 a.m., room: S-439
Dr. Sanjeev Kumar (Indian Institute of Science Education and Research Mohali, India)
Topological transitions in a model for proximity-induced superconductivity
11.12.2019 10:45 a.m., room: S-439
Dr. Markus Eisenbach (Oak Ridge National Laboratory, USA)
Large scale first principles materials calculations using multiple scattering theory

Density functional theory (DFT) calculations have proven to be a useful tool in the study of ground state properties of many materials. Using multiple scattering theory, as pioneered by Korringa, Kohn and Rostocker (KKR), represents an approach with unique capabilities for solving the Kohn-Sham equations of DFT and directly obtain the single particle Green’s function of the system.

I will present our Locally-selfconsistent Multiple Scattering (LSMS) code for scalable large scale first principles density functional calculations of materials. One of the fundamental science drivers for scalable, large scale, first principles calculations of materials is the need to understand states that go beyond periodic crystalline lattices. Due to the large simulation cells of many thousands of atoms needed to describe extended electronic and magnetic orderings, defect states (e.g. extended dislocations, radiation defects etc.) or disorder in alloys, the cubic scaling of traditional first principles calculations methods has prevented direct first principles calculations. By formulating multiple scattering theory in real space, we are able to achieve linear scaling in the number of atoms.

We have demonstrated that these scalable first principles calculations can harnesses the computational power of large massively parallel computers by combining classical Wang-Landau Monte-Carlo calculations with our LSMS code to sample the phase space needed to obtain physical observables as function of temperature. Our approach is able to sample both magnetic or sample chemical order, allowing the first principles calculation of order/disorder phase transitions and phase separations in alloys. Here we will present our method as well as results for magnetism in iron and cementite as well as ordering transitions in binary alloys as well as magnetism in disordered systems.

This research was supported in parts by the Office of Science of the Department of Energy and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory and by the NSF Office of Advanced Cyberinfrastructure and the Division of Materials Research, NSF Directorate of Mathematical and Physical Sciences under award number 1931525. It used resources of the Oak Ridge Leadership Computing Facility, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.

22.1.2020 10:45 a.m., room: S-439
Prof. Dr. Dieter Vollhardt (Universität Augsburg)
The art of modeling in solid state physics & the current state of DMFT
5.2.2020 10:45 a.m., room: S-439
Dr. Saikat Banerjee
Interacting Dirac materials