Kinetic Monte Carlo simulations of Pd deposition and island growth on MgO(100).

Journal Article · Thu May 24 04:00:00 EDT 2007 · Surface Science, 601(14):3133-3142

DOI:https://doi.org/10.1016/j.susc.2007.05.027· OSTI ID:1012315

Xu, Lijun; Campbell, Charles T; Jonsson, Hannes; Henkelman, Graeme A

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The deposition and ripening of Pd atoms on the MgO(10 0) surface are modeled using kinetic Monte Carlo simulations. The density of Pd islands is obtained by simulating the deposition of 0.1 ML in 3 min. Two sets of kinetic parameters are tested and compared with experiment over a 200–800 K temperature range. One model is based upon parameters obtained by fitting rate equations to experimental data and assuming the Pd monomer is the only diffusing species. The other is based upon transition rates obtained from density functional theory calculations which show that small Pd clusters are also mobile. In both models, oxygen vacancy defects on the MgO surface provide strong traps for Pd monomers and serve as nucleation sites for islands. Kinetic Monte Carlo simulations show that both models reproduce the experimentally observed island density versus temperature, despite large differences in the energetics and different diffusion mechanisms. The low temperature Pd island formation at defects is attributed to fast monomer diffusion to defects in the rate-equation-based model, whereas in the DFT-based model, small clusters form already on terraces and diffuse to defects. In the DFT-based model, the strong dimer and trimer binding energies at charged oxygen vacancy defects prevent island ripening below the experimentally observed onset temperature of 600 K.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1012315
• Journal Information: Surface Science, 601(14):3133-3142, Journal Name: Surface Science, 601(14):3133-3142 Journal Issue: 14 Vol. 601; ISSN SUSCAS; ISSN 0039-6028
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BINDING ENERGY
DENSITY FUNCTIONAL METHOD
DEPOSITION
Environmental Molecular Sciences Laboratory
KINETIC EQUATIONS
MAGNESIUM OXIDES
MONTE CARLO METHOD
PALLADIUM
SUBSTRATES
VACANCIES