Theoretical investigation of adsorption of organic molecules onto Fe(110) surface

The adsorption of typical organic molecules onto a clean Fe(110) surface was investigated using density functional theory (DFT). DFT calculations were carried out with the BOP exchange-correlation functional in the DMol3 program. The Fe(110) surface was modeled by using dilayer Fe18 and Fe32 slabs under the periodic boundary condition. The surface relaxation effect was taken into account in calculations using an Fe32 slab. The results show that the order of the molecular adsorption energies is methylamine>methylacetamide>methylacetate, while no bound molecular adsorption structure was obtained for acetic acid, dimethyl ether, or methanol. Accordingly, we conclude that the adhesiveness of organic molecules onto an iron surface may be closely related to the charge transferability of the molecules. The experimental results of X-ray photoelectron spectroscopy in vacuo (methanol on Fe(110) easily dissociates into methoxy and hydrogen fragments even at 100 K and sublimes at 140 K following the adsorption) may correspond to the result of the present calculation, where the adsorbed state of methanol was found to be unstable, in contrast to a previous DFT study, where the adsorption energy of methanol was estimated to be 21.03 kcal/mol.