Chemisorption enhancement of single carbon and oxygen atoms near the grain boundary on Fe surface: ab initio study

The chemisorption of single carbon and oxygen atoms on an iron surface with a Sigma 3(111) grain boundary has been studied by means of first principles modeling. It is shown that adsorption sites close to the grain boundary have higher adsorbability than any site at clean Fe (100), (110), and (111) surfaces. To reveal the mechanism of chemisorption enhancement, several properties are discussed, such as the rearrangement of iron surface atoms, changes in the electronic densities of states, and the spacial charge density differences caused by adsorbates. Due to the higher movability of atoms on the surface near the grain boundary, the chemical bonding of adsorbate to iron atoms in the vicinity of the grain boundary leads to large displacements of surface atoms. The change of the partial density of states of Fe in the vicinity of adsorption sites induced by such rearrangement suggests that the adsorption properties enhancement of the surface is related to the increase of density of states at Fermi level.