| dc.contributor.advisor | Blöchl, Peter E. Prof. Dr. | |
| dc.contributor.author | Sotoudeh, Mohsen | |
| dc.date.accessioned | 2019-05-28T10:15:42Z | |
| dc.date.available | 2019-05-28T10:15:42Z | |
| dc.date.issued | 2019-05-28 | |
| dc.identifier.uri | http://hdl.handle.net/21.11130/00-1735-0000-0003-C01A-7 | |
| dc.identifier.uri | http://dx.doi.org/10.53846/goediss-7480 | |
| dc.language.iso | eng | de |
| dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/4.0/ | |
| dc.subject.ddc | 530 | de |
| dc.title | First-principles calculations of polaronic correlations and reactivity of oxides: manganites, water oxidation and Pd/rutile interface | de |
| dc.type | doctoralThesis | de |
| dc.contributor.referee | Blöchl, Peter E. Prof. Dr. | |
| dc.date.examination | 2018-12-12 | |
| dc.subject.gok | Physik (PPN621336750) | de |
| dc.description.abstracteng | The electronic, magnetic and atomic structure of Pr1−xCaxMnO3 have been investigated using combination of first-principles calculations, x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and electron-energy loss spectroscopy (EELS). With the compositions x = 0, 1/2, and x = 1 and variety magnetic orders, we cover the entire doping range. Jahn-Teller as well as Zener polaron orders are considered. The comparison of experimental data with calculated spectra opened up new insight far beyond of the individual techniques.
We use local hybrid functionals in our calculations to account for the Coulomb interaction on the Mn-sites and to obtain the physically correct description of the electronic structure. With the local hybrid functional we avoid the well known deficiencies of density-functional calculations, which do not account explicitly for the strong Coulomb interaction in the Mn-d shell. The free parameters of the local hybrid functionals have been determined by comparison with measured XPS spectra. The obtained admixture of the Fock-term is substantially smaller than the value suggested on the basis of perturbation theory. For Pr1/2Ca1/2MnO3 we have explored two distinct magnetic orders, CE and E-type, with low energy, which exhibit a similar band gap.
With obtained hybrid factors, we investigated the electronic structure of La1−xSrxMnO3 with first-principles calculations. With the compositions x = 0, 1/3, and x = 1 the entire doping range have been covered. Jahn-Teller polaron as well as half-metallic system are considered. The comparison of Pr1−xCaxMnO3 and La1−xSrxMnO3 provides a detailed and deep understanding of manganites.
Passing from bulk to surface, a number of competing mechanisms for water splitting reactions are discussed. The role of correlated processes and fluctuations of the catalyst surface in contact with water are explored. Based on the dimeric water, we suggested a mechanism for oxygen evolution reaction on CaMnO3 (001) surface. The calculated DoS and orbital representations shed lights on the reactions steps. The energetic shows more stability for hemibonding interaction compared to the proton transfer. We demonstrated that lattice oxygen participation is unlikely for CaMnO3 (001).
To shed light on defects that play roles in the physical and chemical properties of metal
oxides, a common native point defect, oxygen vacancy, and its combination with hydrogen in the well-known metal oxide TiO2 are studied. We demonstrate that in contact with palladium (Pd) under exposure of hydrogen, the interstitial hydrogen and the hydrogen-oxygen vacancy complex are actually positively charged and more stable. With these simulations, changes in EEL spectra collected experimentally in the vicinity of Pd/TiO2 interface are explained. | de |
| dc.contributor.coReferee | Jooß, Christian Prof. Dr. | |
| dc.subject.eng | density functional theory, manganites, Pr1−xCaxMnO3, La1−xSrxMnO3, TiO2, spectroscopy, electronic structure, water splitting, native point defect | de |
| dc.identifier.urn | urn:nbn:de:gbv:7-21.11130/00-1735-0000-0003-C01A-7-6 | |
| dc.affiliation.institute | Fakultät für Physik | de |
| dc.identifier.ppn | 1666651826
1666649023 | |