Doctoral College TU-D Unravelling advanced 2D materials
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Theoretical materials chemistry in low dimensions

Peter Blaha, Institute of Materials Chemistry

Theoretical calculations provide the basis for the understanding of electronic, magnetic, optical or mechanical properties of matter and thus are essential for the development of functional materials. Most of the current state-of-the-art theoretical methods for solids, surfaces and interfaces are based on density functional theory (DFT). The resulting Kohn-Sham equations need to be solved efficiently on a computer. Over the last 30 years the PB group has developed WIEN2k, a “Full-potential augmented-plane-wave plus local orbitals” program package. This code has become one of the most widely used programs for simulations of solid state properties (more than 2550 registrations worldwide) and is in particular known for its high accuracy and reliability. It allows for an efficient structural optimization and then calculates the electronic (and magnetic) structure of a solid. Furthermore WIEN2k can interpret/predict various spectroscopic properties including STM, optical absorption, UPS, XPS (core level shifts), XANES, EELS, Mössbauer, NMR and IR or Raman spectra. The group has applied this method to various materials science problems, in particular also to surfaces and multilayer systems.

 

 

PhD Project 1: Fe-oxide surfaces

Co-supervisor:  Gareth Parkinson

The (100) surface of magnetite Fe3O4 is a very interesting and challenging system of technological importance. Only recently a correct structural model has been put forward and verified by joined theoretical and experimental efforts. The surface of magnetite can be used as template for the adsorption of various metal ad-atoms and the adsorption behavior can vary from forming very stable single ad-atoms (Au) to more mobile species with fairly easy cluster formation. In addition some atoms enter the surface and occupy vacant sites. These systems can be further studied under the influence of various molecules (O2, H2O, CO) investigating possible relevance for catalysis. Another interesting surface is the (012)-Fe2O3 surface, which will be studied in detail. Intense collaboration and thus close connections to experiment is foreseen for both systems with the GP group.

PhD Project 2: Carbon based nanostructures

Co-supervisor:  Dominik Eder


The modification of carbon-based nanostructures (fullerenes, nanotubes, graphene) by doping or in combinations/contact with inorganic materials may lead to specific functionalization and various new properties. DFT based simulations of such systems provide the basis for a deeper understanding of these complicated systems. The first step is always a structure relaxation as the detailed structures of such systems are often not known experimentally. In case that STM, AFM or TEM studies of such systems exists, theory may help in the interpretation of these experiments. Afterwards one can explore the electronic structure and simulate various spectroscopies like NMR, XPS, XANES,EELS or optical spectroscopy which should show unique features due to the modified bonding neighbors. The calculation of XANES and EELS involves excited states of core electrons and huge excitonic features, which can be modelled by core-hole supercell calculations or solving a 2-particle (electron-hole) problem using the Bethe-Salpeter approach [PB05].  


Literature

  1. P. Blaha, et al.: WIEN2k: An augmented plane wave plus local orbitals program for calculating crystal properties. K.Schwarz, TU Wien, ISBN 3-9501031-1-2 (2001) www.wien2k.at
  2. H. Dill, J. Lobo-Checa, R. Laskowski, P. Blaha, S. Berner, J. Osterwalder, T. Greber, Science 319, 1824 (2008) DOI:10.1126/science.1154179
  3. R. Bliem, et al.: Science 346, 1215 (2014) DOI: 10.1021/10.1126/science.1260556
  4. E. Assmann, P. Blaha, R. Laskowski, K. Held, S. Okamoto, G. Sangiovanni: Physical Review Letters 1108, 078701 (2013) DOI:10.1103/PhysRevLett.110.078701
  5. F. Karsai, F.P. Tiwald, R. Laskowski, F. Tran, D. Koller, S. Gräfe, J. Burgdörfer, L. Wirtz, P. Blaha: Physical Review B 89, 125429 (2014) DOI:10.1103/PhysRevB.89.125429