Vibrational dynamics of H atoms chemisorbed on metal (110) surfaces

The dynamical properties of a hydrogen atom chemisorbed at a site of trigonal symmetry on a (110) metal surface are studied by classical trajectory calculations. A model potential is used which is highly anharmonic, and which includes many realistic features present in the case of H on W(110). The calculations show that periodic, quasi-periodic and chaotic trajectories all play significant roles in the dynamical properties of the system at the temperatures of interest. The power spectrum is computed, and the resulting frequency structure is in semi-quantitative accord with recent experimental data on the parallel vibrations of H on W(110). Implications of the results as to the properties of the H/metal surface potential and of the related frequency spectrum are discussed.