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Interpretation of palladium XANES spectra from first principles calculations

Johan Nilsson (Institutionen för kemi och kemiteknik, Teknisk ytkemi ; Kompetenscentrum katalys (KCK)) ; Per-Anders Carlsson (Institutionen för kemi och kemiteknik, Teknisk ytkemi ; Kompetenscentrum katalys (KCK)) ; Henrik Grönbeck (Institutionen för fysik, Kemisk fysik (Chalmers) ; Kompetenscentrum katalys (KCK)) ; Magnus Skoglundh (Institutionen för kemi och kemiteknik, Teknisk ytkemi ; Kompetenscentrum katalys (KCK))
Topics in Catalysis (accepted) (2016)
[Artikel, refereegranskad vetenskaplig]

Ab-initio X-rayabsorptionnearedgestructure(XANES)spectrawerecal- culated for palladium model systems of importance in catalysis to investigate the effects of size, structural motif and oxidation state. Palladium nanoparticles with dif- ferent size, structural motifs, and oxygen coverage were constructed and their struc- ture relaxed using conventional plane-wave density functional theory calculations. Pd K-edge XANES spectra were calculated using the real-space multiple scattering formalism. The results show that the Pd-Pd distances are slightly compressed in the smaller nanoparticles leading to peak shifts in the XANES spectra, the amplitude of the fine structure oscillations increases with the average coordination number. Fur- thermore, Pd nanoparticles with different structure motifs exhibit XANES spectra that show high resemblance. The calculations show that adsorbed oxygen increases the intensity in the XANES spectrum between the first and the second absorption peak, corresponding to the initial development of a whiteline peak. A bulk like struc- ture where Pd coordinates to four oxygen atoms is necessary to achieve a strong whiteline peak.



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Denna post skapades 2016-03-20. Senast ändrad 2016-03-22.
CPL Pubid: 233449