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Seminar by Dr. Letizia Chiodo

Center for Life Nano Science @ Sapienza, Rome (Italy)

20 Apr 2015 14:00
20 Apr 2015 15:00
Lecture room 2009, Jülich GRS building (16.15)

Transition metals oxides, from extended systems to nanostructures: ab initio electronic and optical properties

The electronic and optical behavior of TiO2 and ZnO is of foremost importance in both fundamental science and technological applications including photocatalysis and photovoltaics. The theoretical methods and computational tools provide interesting results, clarifying and interpreting experimental data, with an added strong predictive power concerning the optical response of specifically designed systems.

The electronic properties and optical spectra of nanostructured metal oxides are presented in this seminar, including atomic clusters, nanowires, nanoclusters and nanosheets, without disregarding the extended bulk phases. Given the electronic complexity of the materials, the clear theoretical description of their bulk basic properties provides indeed interesting insights both from the solid state physics and the chemistry point of view.

An effective combination of molecular dynamics, density functional theory, and excited states theories (time dependent density functional theory - TDDFT, and many body techniques, in the GW+BSE approximation scheme) is used to obtain the response of oxides structures under external exciting fields.

Results from the two excited states methods, namely TDDFT and GW+BSE results, are compared for smallest nanoclusters, clarifying the role of the different physical contributions embedded in the two theories. Ab-initio optical spectra are shown to be critical for identifying the crystal phases of experimental nanostructure samples. The role of doping defects, phonon vibrations and organic adsorbates is also investigated, assessing the high quality description of the ab initio methods for such materials, and their great predictive power.