Pt adsorption on the PbTiO3(110) polar surface: A density functional theory study

The monolayer (ML) and submonolayer Pt on both terminations of PbTiO3(110) polar surface have been studied by using density functional theory (DFT) with projector-augmented wave(PAW) potential and a supercell approach. The most favored ML Pt arrangements on PbTiO and O-2 terminations are the hollow site and the short-bridge site, respectively. By examining the geometries of different ML arrangements, we know that the dominant impetus for stability of the favored adsorption site for PbTiO termination is the Pt-Ti interaction (mainly from covalent bonding), while that for O-2 termination is the Pt-O interaction (mainly from ionic bonding). In addition, the appearance of the gap electronic states in the outermost layers of each termination indicates that a channel for charge transfer between adsorbed layer and substrate is formed. Moreover, the interface hybridization between Pt 5d and O 2p orbitals is also observed, especially for ML Pt on O-2 termination. The stability sequences for various arrangements of 1/2 ML Pt adsorption conform well with those of ML Pt adsorption, and the most stable arrangement is energetically more favorable than the corresponding ML coverage in the view of adsorption energy maximization. The behavior, i.e. the increase in adsorption energy with decrease in coverage, indicates that Pt-Pt interactions weaken those between Pt and the substrate. Copyright (C) 2009 John Wiley & Sons, Ltd.