Bonding of Pt/Fe overlayer and its effects on atomic oxygen chemisorption from density functional theory study

First principles spin-polarized total energy calculations using density functional theory (DFT) within generalized gradient approximation (GGA) were performed to investigate the electronic structure of Pt monolayer on Fe(0 0 1) and the bonding at Pt-Fe and its effect on O atom chemisorption. Layer by layer density of states (DOS) for Pt/Fe(0 0 1) against the reference systems, unreconstructed Pt(0 0 1) and Fe(0 0 1) show a peak of Pt d states at the Fermi level and a spin polarization of Pt dzz states. Charge redistribution at Pt-Fe interface shows charge transfer from the Pt and Fe atom sites towards the Pt-Fe bonds verifying strong bimetallic bonding. Similar charge redistribution is observed for Pt(0 0 1) with increase in charges at surface Pt-Pt bonding sites. Binding energies of adsorbed O on the three high symmetry sites follow the order: top < hollow < bridge. The efficiency of Pt d-electron back donation to adsorbed O on bridge is driven by a more localized bonding of O atom on this site. This mechanism of electron back donation may also be utilized in rationalizing the observed weakened binding of O on Pt/Fe system as compared to clean Pt(0 0 1) along with the d-band center model.