CLUSTER ADSORPTION ON METALLIC SURFACES - STRUCTURE AND DIFFUSION IN THE CU/PD(110) AND PD/PD(110) SYSTEMS

We investigate structural and diffusion properties of CuN and PdN (with N going from 1 to 30) clusters adsorbed on the (110) surface of Pd via atomistic simulations performed by employing embedded atom method potentials. For both systems, one dimensional linear chains are lower in energy than two dimensional structures, although the linear chain stability is more enhanced in the case of Cu/Pd(110). Our results on cluster stability are analyzed in terms of effective interactions and adsorbate arrangement upon relaxation. In close connection with STM experiments performed recently on Cu/Pd(110) [Roeder et al., Nature 366, 141 (1993)] we evaluate the diffusion barrier for atomic movement along and across the [11̄0] direction. A cross exchange mechanism is found to lower significantly the diffusion barrier across the [11̄0] direction, consistent with the value of the diffusion anisotropy found experimentally and the phase separation observed at the uppermost layer level. © 1995 American Institute of Physics.