Vibrations of small cobalt clusters on low-index surfaces of copper: Tight-binding simulations

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Vibrational properties (frequencies, polarizations, and lifetimes) of a single adatom, dimer, and trimer of Co on low-index Cu surfaces, Cu(111), Cu(001), and Cu(110) are studied by using tight-binding second moment approximation interatomic interaction potentials. We show that structural and vibrational properties of the Co clusters strongly depend on the substrate orientation. The longest lifetimes of 1--2.5 ps have been found for high-frequency z-polarized vibrations in all the Co clusters considered. The shortest lifetimes of 0.1--0.8 ps have been obtained for low-frequency horizontal (frustrated translation) vibrational modes.