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Diffusion of palladium clusters on magnesium oxide.
G Barcaro1, A Fortunelli, F Nita
1IPCF/CNR, Via Alfieri 1, Ghezzano, I56010, Italy.
Physical Review Letters
|December 31, 2005
Summary
Small palladium clusters move faster than single atoms on MgO(100) via novel mechanisms. This fast cluster diffusion is key to understanding palladium aggregate growth in experiments.
Area of Science:
- Surface science
- Materials science
- Computational chemistry
Background:
- Understanding the behavior of small metal clusters on oxide surfaces is crucial for catalysis and thin-film growth.
- Palladium (Pd) clusters on magnesium oxide (MgO) are model systems for studying metal-support interactions.
Purpose of the Study:
- To theoretically investigate the diffusion mechanisms of small palladium clusters on the MgO(100) surface.
- To correlate theoretical diffusion findings with experimental observations of palladium aggregate growth.
Main Methods:
- Density Functional Theory (DFT) calculations were employed to model palladium cluster diffusion.
- Analysis of various diffusion pathways including dimer rotation, trimer walking, tetramer rolling, and sliding.
Main Results:
- Small palladium clusters exhibit surprisingly fast diffusion rates on MgO(100), exceeding those of isolated adatoms.
- Novel diffusion mechanisms, such as rolling and walking, were identified for small clusters.
- Fast cluster mobility is essential for explaining the observed growth of palladium aggregates.
Conclusions:
- The theoretical model accurately reproduces experimental results when fast cluster diffusion is considered.
- The mobility of palladium clusters, not just individual atoms, plays a critical role in the initial stages of palladium film formation on MgO(100).