Ab initio density functional theory studies on oxygen stabilization at the V2O3(0 0 0 1) surface

Geometric and electronic details of the V′OV and VV′O terminated V2O3(0 0 0 1) surface after oxygen chemisorption are studied theoretically by density-functional theory using large cluster models. Adsorption of oxygen above vanadium centers of the V′OV terminated surface (OtV′O termination) results in very strongly bound vanadyl groups removing part of the relaxation of the initial adsorbate-free surface. In addition, it affects the oxygen 2p dominated valence band region of V2O3(0 0 0 1) which increases its width by 1.5 eV due to the adsorbate, as shown in partial densities-of-states curves. Oxygen adsorption between vanadium centers of the VV′O terminated surface is considered for coverages Θ(Ob)=1/3 and Θ(Ob)=2/3 yielding terminations ObVV′ and Ob2VV′. For both coverages the adsorbate stabilizes above the surface and forms V′–Ob–V bridges. As before, the adsorption removes part of the perpendicular relaxation of the topmost layers at the initial VV′O terminated surface. In addition, the V–Ob–V′ bridges lead to decreased lateral distances between the corresponding V/V′ centers. As a result, the lateral honeycomb geometry of the combined V/V′ layers of the VV′O termination is distorted by adsorbed oxygen where the distortion leads to different surface patterns for the ObVV′ and Ob2VV′ termination. The theoretical analysis suggests that only the Ob2VV′ termination, corresponding to an oxygen coverage Θ(Ob)=2/3, is compatible with the geometry obtained from STM images of V2O3(0 0 0 1) films on Cu3Au(0 0 1).