Effect of S arrangement on Fe(110) properties at 1/3 monolayer coverage: a DFT study

Using density functional theory calculations, we compare the relative stabilities and properties of different arrangements of S on Fe(110) at a 1/3 monolayer coverage, including two observed experimentally. For all studied arrangements, S is adsorbed in the three high-symmetry adsorption sites: 4-fold hollow, 3-fold hollow, bridge, and atop sites. The binding energy, work function change, adsorption geometry, charge density distribution, magnetic properties, and density of states are determined and compared. The most stable overlayer arrangement corresponds to the overlayer seen by experiment after dissociative adsorption of H2S and has S adsorbed in 4-fold hollow sites. In the other arrangements, the S atoms are located closer to each other on the surface reducing the stability of the overlayer. S causes a minor adsorbate-induced reconstruction of the Fe surface and quenches the magnetic moment of the Fe atoms it bonds to directly. It adsorbs as an electropositive species, causing a positive work function change and forms polar covalent bonds to the surface.