Zigzag chain structures of Gd on the Mo(1Â 1Â 0) surface

Structures of Gd adsorbed layers on the Mo(1 1 0) surface have been investigated by LEED and STM methods. In general, the structures of Gd layers are found to be similar to those observed for various rare earth metals on (1 1 0) surfaces of bcc transition metals, but at low Gd coverages demonstrate a rich amount of dilute (n × 2) structures, which can be explained as forming zigzag chains oriented along the [11¯0] direction. Remarkably large spacing between the chains, up to 35 Å, has been observed for the most dilute (22 × 2) structure. First-principle DFT calculations indicate that at low coverage Gd atoms occupy quasi threefold hollow sites on the Mo(1 1 0) surface and that forming zigzag chains correspond to lower total energy with regard to a uniform distribution of linear chains. Forming chain structures are suggested to be a result of indirect lateral interaction between Gd adatoms. Performed Monte Carlo simulations provide clear evidence in support of this interpretation.