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(001) and the bonding at Pt-Fe and its effect on O atom chemisorption. Layer by layer density of states (DOS) for Pt/Fe(001) against the reference systems, unreconstructed Pt(0011) and Fe(001)show a peak of Pt d states at the Fermi level and a spin polarization of Pt d(zz) 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(001) 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 cl-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(001) along with the d-band center model. (C) 2008 Elsevier B.V. All rights reserved.