Face Centered Cubic Transition Metal Surface Vibrations
We calculate the surface atom and adatom positions or vibration spectra from the electronic structure. The valence bands are described in the tight-binding approximation. We fit the d band parameters to bulk properties. The clean surface atomic positions are obtained by a direct minimization of the crystal energy. The agreement with the experimental results is quite good. All the clean surfaces are found to be contracted. The effect of this contraction on the surface vibration spectra is studied. The contraction increases with the surface roughness. It enhances the force constants between the atoms close to the surface leading to localized step vibrations above the bulk frequency spectrum. The model is also extended to chemisorbed chalcogenide atoms. The experimental positions and vibration frequencies are fitted. Then we can study the influence of chemisorption on the surface relaxation or vibrations and also the elastic indirect interaction between adatoms.
KeywordsCohesive Energy Nickel Surface Surface Relaxation Face Center Phonon Dispersion Curve
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