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PGI-1 Talk: Dr. Sergii Khmelevskyi
Ab-initio based modelling of magnetic interactions in solids
- begin
- 14 Nov 2018 11:30
- venue
- PGI Lecture Hall
Vienna University of Technology, Austria
Abstract:
Conventional methods of the modern ab-initio electronic structure theory, like LSDA and its extensions, deal with ground state properties of the solid materials at zero temperature. In order to explore finite temperatures properties, in particular, order-disorder phase transition, one need in addition to supply the model that mimics the most important features of the system behavior and then to calculate the model parameters from the ab-initio with a properly chosen set of physical constraints. I will argue that there is no unique first-principle recipe how to deal with all magnetic materials on equal footing. The magnetic materials might be sub-divided into the three major classes that requires special approaches and has specific problems, but also allowing for specific simplifications. This classes are magnetic insulators, 4f-metals with high degree of the magnetic moment localizations and d-metals and intermetallic compounds and alloys. For the first classes an important role of the correlation effects are evident, but quantum Heisenberg model with some modifications provide robust description of the finite temperature magnetic properties. The class of the d-metallic systems is less correlated but the construction of the proper magnetic model is difficult since the spin moments fluctuates s also in their magnitude. The 4f-metals are intermediate case where localized correlated shells coexists with non-correlated conduction band that mediates inter-site interactions. In the talk I will illustrate how one can deal with specific problems of these classes of materials using as examples oxides with complex magnetic order ( e.g. Sr2RuO4, UO2), canonical 4f and 3d ferromagnetic metals -hcp Gd, bcc Fe and fcc Ni, some functional magnetic alloys , and intermediate hybrid case of DyCo5. The novel approach for ab-initio based modelling of the longitudinal spin-fluctuations in metals and examples of the magnetic multistate simulations will be presented.
Contact
Prof. Dr. Stefan Blügel
