DFT insights into the adsorption mechanism of five-membered aromatic heterocycles containing N, O, or S on Fe(1 1 0) surface

Understanding the interaction of five-membered aromatic heterocycles with Fe(1 1 0) surface is crucial to the design of novel inhibitors against the corrosion of iron and steel. Herein, we report a detailed study of the adsorption properties and the bonding mechanism of pyrrole, furan, and thiophene on Fe(1 1 0) surface employing density functional theory (DFT) calculations. In the most stable adsorption geometries, the adsorbates lie flat at the hollow site and form covalent bonds with surface Fe atoms. The chemisorptions are demonstrated by large adsorption energies and charge transfers from Fe(1 1 0) to the adsorbates. Taking vdW corrections into account in the DFT calculations has a minimal effect on the adsorption geometries whereas it significantly increases the adsorption energies. The energetic and structural analysis demonstrates large molecular distortion induced by the adsorbate–surface interaction, and thiophene experiences the least molecular distortions, thereby having the largest adsorption energy among the adsorbates. The electronic structure analysis reveals that the electronic interactions of pyrrole, furan, and thiophene and Fe(1 1 0) are due to the overlaps of the frontier molecular orbitals with Fe-3dz2 and Fe-(3dxz + 3dyz) states. The charge transfer between the adsorbates and Fe(1 1 0) are elucidated by the charge density difference plot and Bader charge analysis.