Ph.D. Research Info

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From June 1^st 2000 I'm a Ph.D. student at the Laboratory of Inorganic Chemistry and Catalysis (part of the Schuit Institute of Catalysis, SKI) of the Eindhoven University of Technology.

E-Mail: willy@brilsmurf.chem.TUe.nl

Periodic DFT-calculations on the catalytic oxidation of ammonia

W. K. Offermans, A. P. J. Jansen, G.-J. Kramer and R. A. van Santen
Schuit Institute of Catalysis, Eindhoven University of Technology,
P.O. Box 513, SKA, 5600 MB Eindhoven, The Netherlands

Despite numerous investigation, there are a lot of uncertainties about the catalytic oxidation of ammonia[1, 2]. The goal of our research is to determine the role of oxygen and steps on a Pt-surface in the activation of ammonia. In order to achieve this, electronic structure calculations within a DFT-framework are performed with the VASP-code[3, 4]. A slab, consisting of 5 layers of Pt-atoms and separated by 5 layers of vacuum in a 2x2 supercell approach, serves as a model for the catalyst. Adsorbates, like NH₂, OH, NO etc., which are likely to be involved in the catalytic oxidation of ammonia over platinum, are investigated on different surf aces like Pt{111} and Pt{211}. We are particularly interested in:

• optimized geometries
• binding site preferences and binding energies of adsorbates and co-adsorbates
• transition states of surface reactions; geometries as well as energies of those states
• data points (energy vs. atom coordinates) around the minima and transition states to determine pre-factors for surface reactions

As an illustration, the dissociation of ammonia at the step edge of Pt{211}: reactant-, transition- and product-state

As an illustration, the dissociation of ammonia at the step edge of Pt{211}: reactant-, transition- and product-state

En passant, we looked to the possibility to determine lateral interactions for adsorbed oxygen on the Pt{111}-surface. The values for the lateral interactions were used in a Dynamic Monte Carlo simulation to mimic the desorption of oxygen from the Pt{111}-surface[5].

Bibliography

[1] J. M. Bradley, A. Hopkinson, and D. A. King, Journal of Physical Chemistry 99, 17032 (1995).

[2] W. D. Mieher and W. Ho, Surface Science 322, 151 (1995).

[3] G. Kresse and J. Furthmüller, J. Comp. Mat. Sci. 6, 15 (1996).

[4] G. Kresse and J. Furthmüller, J. Phys. Rev. B 54, 11169 (1996).

[5] A. P. J. Jansen and W. K. Offermans, Journal of Computational Methods in Science and Engineering 2, 43 (2002).

• Reaction rate constants via computer calculations