MODEL CLUSTER STUDIES OF THE RESTRUCTURING OF THE FE(110) SURFACE-INDUCED BY THE ADSORPTION OF CARBON, NITROGEN OR OXYGEN

The EHT method has been used to calculate the energy of iron clusters, Fe-11, modelling the Fe(110) surface, as well as the energy of iron c lusters with oxygen (Fe-11-O), nitrogen (Fe-11-N), or carbon atom (Fe- 11-C), adsorbed on a reconstructed or non-reconstructed surface. To de termine the relative positions of iron atoms and of the adsorbed atom a sphere model was employed assuming displacement of only one iron ato m. ENT calculations show that the most preferential sites for oxygen, Nitrogen and carl,on adsorption are located on the non-reconstructed F e(110) surface. The conceivable transition to the underlayer adsorptio n state would be an activated process. The activation energy for that transition for carbon atoms would be the greatest and for nitrogen ato ms - the smallest one. The energy difference between the overlayer and underlayer adsorption state ranges in the sequence of increasing atom ic number, The results are compared with calculations made earlier for (111) and (100) iron surfaces.