DYNAMICS OF MOLECULAR-SURFACE DIFFUSION - ENERGY-TRANSFER BETWEEN ADSORBATE MODES

Diffusion of model rigid, linear triatomics adsorbed on a Ni(111) surf ace has been simulated by molecular dynamics. Changing the mass distri bution in the model triatomic permits variations in the bending freque ncy without altering the potential. Thus, dynamical effects of bending on surface diffusion can be studied in isolation from thermodynamic e ffects. Diffusion coefficients and mean-squared hop lengths increase l inearly with the bending frequency. Translational and rotational modes are strongly coupled. As the bending frequency of the adsorbate decre ases, transfer of lateral translational energy to rotational energy be comes more effective, and correlation between the rotational and trans lational modes becomes stronger. At lower bending frequencies, energy transfer to the molecular bending mode is the dominant mechanism for t he dissipation of lateral translational energy.