Nitrogen adsorption on Fe(111), (100), and (110) surfaces

Adsorption energies and structures for N atoms on three low-index surfaces of Fe have been calculated using density functional theory (DFT) and the ge neralized gradient approximation (GGA). At low N coverage the adsorption en ergy on Fe(100) is found to be similar to 0.7 eV higher than on the (111) a nd (110) surfaces - particularly the c(2 x 2)-N/Fe(100) structure with the N atoms in four-fold sites is very stable. We attribute the differences in adsorption energy to the lack of four-fold sites on the (111) and (110) sur faces, We suggest that at higher N coverages, islands with a structure simi lar to the c(2 x 2)-N/Fe(100) structure will form on the (111) and (110) su rfaces. (C) 1999 Elsevier Science B.V. All rights reserved.