Abstract
Using ab initio density-functional perturbation theory the lattice dynamics of the O-bridge terminated surface has been extensively studied. Excellent agreement with high-resolution electron-energy-loss spectroscopy measurements was obtained. It was found that the surface is unstable over a wide range of reciprocal-lattice vectors. This suggests that substrate and/or defect influence play a more important role for the stability of the structure than thought so far, with important consequences for catalysis. A stable reconstruction was found which allowed a reliable determination of the vibrational contribution to the surface-free energy. Comparing these results with estimates based on a very simple Einstein model the ab initio results can be reproduced only by assuming an ad hoc 50% decrease of the Einstein mode frequency at the surface. This clearly demonstrates the need for an ab initio treatment of the vibrational surface-free energy to obtain reliable phase diagrams for catalysis.
- Received 7 October 2009
DOI:https://doi.org/10.1103/PhysRevB.81.081405
©2010 American Physical Society