Self-diffusion behaviors of Pd adatom and dimer on Pd(0 0 1) surface

Using molecular dynamics simulations and a modified analytic embedded atom potential, the self-diffusion dynamics of Pd adatom and dimer on Pd(0 0 1) surface have been studied in the temperature ranges from 600 K to 900 K. The simulation time varies from 25 to 50 ns according to the different substrate temperature. The diffusion mechanism of both the single Pd adatom and dimer is the simple exchange mechanism with the substrate atoms. The diffusion prefactors D0 and activation energies Ea are derived from the Arrhenius relation. The activation energy Ea is in good agreement with the result of the quench molecular dynamics and experimental data of the single Pd adatom. The activation energy 0.58 ± 0.02 eV of the dimer is slightly lower than that 0.63 ± 0.02 eV of the single adatom because of the higher coordination numbers. When substrate temperature T = 290 K, the diffusion mobility D of the single adatom is equal to that of the dimer. In addition, the remarkable self-diffusion behaviors in several previous experiments that the diffusion mobility of the dimer is higher than that of the single adatom at low temperature are explained according to our molecular dynamics results.