Periodic DFT Study of the Pt(111): A p(1×1) Atomic Oxygen Interaction with the Surface

Abstract

The p(1×1) adsorption of atomic oxygen on the fcc and hcp three-fold hollow site of a Pt(111) surface has been investigated by a periodic slab model, varying the number of layers from two to four. The density functional method with local spin density approximation and with generalized gradient exchange−correlation functionals was employed using the CRYSTAL95 ab initio program. It was found that the three-layer slab model was a good compromise between accuracy and the computational time. The LDA/VWN calculations predict that the fcc-hollow site is energetically preferable by 0.29 eV compared to the hcp-hollow site. This preference is also supported by experimental data. Oxygen p(1×1) heat of adsorption of 0.61 eV calculated with the BPW91 method is in reasonable agreement with the experimentally estimated one. The corresponding equilibrium adsorbate−surface distance is 1.25 Å. Density-of-states analysis demonstrates that the formation of the Pt−O bond is mainly due to the interaction of Pt 5dxz and 5dyz orbitals of the surface platinum atom and 2px and 2py orbitals of the oxygen adatom. Three-dimensional difference electron density plots indicate a delocalized interaction of the oxygen adatoms to the surface.