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Parameter free calculations of solid-state excitations & spectra: Fiction or reality
Friedhelm Bechstedt
Friedrich-Schiller-Universität Jena
Fri, May. 15th 2009, 10:30
Amphi. Becquerel, École Polytechnique, Palaiseau, Institut Polytechnique de Paris (IPP), Palaiseau
The dream of computational physicists is to compute materials properties from first principles without taking any parameter from experiment. The prize that has to be paid in its realization is the inclusion of all important interactions between nuclei and electrons in the investigated many-body systems. In the talk the realization of the dream is illustrated for electronic excitations and related measurable spectra. The progress in the field but also the limitations are discussed for bulk oxides and nitrides which play an important role for electronics, optoelectronics, and photovoltaics. Based on optimized atomic geometries charged electronic excitations can be described within the quasiparticle approach with an accuracy of about 0.1 eV. This holds not only for energy gaps but also for the prediction of photoemission as well as X-ray absorption spectra. The talk shows that the lineshape of optical spectra can indeed be predicted if the electron-hole coupling is taken into account beyond the quasiparticle approach. Examples are given not only for bulk systems but also for nanomaterials. Pr. Friedhelm Bechstedt is responsible of one node of the ETSF (European Theoretical Spectroscopy Facility.
Contact : Nadege OLLIER

 

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