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This project was finished with a set of publications, and a successful Ph.D. thesis defence.

For the most up-to-date information about this PhD work, go to Paul's personal research pages.

Transition metal surfaces show reconstruction under adsorption and roughening under reaction conditions. An extreme case is catalytic etching, which can be identified as such by the fact that no (or much less) roughening occurs when either of the reactants is removed under otherwise identical conditions. This phenomenom was first described in detail by Schmidt in 1974 for platinum under conditions of ammonia oxidation [1]. We feel that better understanding of these processes are essential to the development of practical catalysts as the issue is closely related to catalyst stability.

Fundamental understanding into this phenomenom is lacking and is hardly studied in detail on the theoretical side. The ultimate aim is then to understand on a molecular level the processes involved. In order to achieve this goal, one must rely on an effective potential method. We chose the Modified Embedded-Atom Method (MEAM) as developed by Baskes and co-workers [2,3]. In contrast with Baskes and co-workers, we do not obtain the values for the parameters involved from experiment (which leaves considerable arbitrariness), but from DFT calculations. Therefore, we have developed an efficient scheme for obtaining the parameters unambiguously, which correctly describe a wide range of bulk and surface properties.

For the DFT calculations we use the VASP package [4], which solves the Kohn-Sham Hamiltonian with a plane-wave basis set and ultrasoft Vanderbilt pseudopotentials. The MEAM MM/MD calculations are performed with both the DYNAMO package by Baskes and co-workers [2,3] and with the CAMELION package by Thijsse and co-workers [5].

At this point we have developed potentials for the fcc-metals Rh, Pd, Ir, and Pt and tested them on various systems (e.g., self-diffusion barriers and surface reconstructions). These results, including the parameterization scheme and a new physical interpretation of the MEAM, have been published in the Physical Review B [6].

1. R.W. McCabe, T. Pignet, and L.D. Schmidt, J. Catal. 32, 114 (1974).
2. M.I. Baskes, Phys. Rev. B 46, 2727 (1992).
3. M.S. Daw and M.I. Baskes, Phys. Rev. Lett. 50, 1285 (1983); M.S. Daw and M.I. Baskes, Phys. Rev. B 29, 6443 (1984).
4. G. Kresse and J. Furthmüller, Comp. Mat. Sci. 6, 15 (1996); G. Kresse and J. Furthmüller, Phys. Rev. B 54, 11169 (1996).
5. CAMELION is a joint product of ComMaS and CRI->SIS, both at Delft University of Technology, Faculty of Applied Sciences, Laboratory of Materials Science. Contact person is Prof. Dr. B.J. Thijsse.
6. P. van Beurden and G.J. Kramer, Phys. Rev. B 64, 165106 (2001).

These pages are maintained by Bouke Bunnik (B.S.Bunnik@tue.nl). Comments and suggestions are welcome.