Comparison of c(2 x 2) N/Fe(001) and Fe4N(002) surfaces:: a density-functional theory study

By using first-principles density-functional theory calculations, we compare the properties of c(2 x 2) N/Fe(001) with the Fe4N(002) surface possessing Fe2N stoichiometry. We observe a number of similarities as far as the geometry, bond lengths, local density of electronic states and magnetic moments in the surface region are concerned. However, for c(2 x 2) N/Fe(001) the shortest interatomic distance is between N and subsurface Fe atoms, whereas for Fe4N(002) the shortest bond is formed between N and surface Fe atoms, which leads to some important differences. In particular, the magnetic moments are higher for the c(2 x 2) N/Fe(001) surface Fe atoms than for the Fe4N(002) ones, and the opposite is true for the subsurface Fe atoms.