Lateral interactions and zigzag chains of Ho on the Mo(110) surface

The structure of Ho adsorbed layers on the Mo(110) surface has been studied by low energy electron diffraction (LEED) and scanning tunneling microscope (STM). It has been found that at submonolayer coverages Ho atoms, similarly to studied earlier Gd and Nd, form a rich amount of dilute (n × 2) commensurate structures built from zigzag chains oriented along the 11?0] direction. The formation of zigzag chain structures is initiated by the indirect lateral interaction between adsorbed Ho atoms, which, as is illustrated by Monte Carlo simulations, can be well approximated by a screened Coulomb potential superimposed with Friedel oscillations.