Density functional theory analysis of the Ni(1 1 0)c(2 × 2)-CN surface phase

Density functional theory slab calculations have been used to investigate the structure of the Ni(1 1 0)c(2 × 2)-CN adsorption phase. The results show excellent agreement with experimental quantitative determinations of this structure by photoelectron diffraction and low energy electron diffraction. In particular, they show that a lying-down orientation with the C-N axis along [0 0 1] perpendicular to the close-packed [1¯10] Ni rows on the surface is strongly favoured over end-on adsorption (with the C-N axis perpendicular to the surface). This geometry is also favoured over a lying-down geometry with the C-N axis aligned along the [1¯10] azimuth, as originally proposed for this system and supported by cluster calculations.