Tight binding model of induced band shift in CoO nanoparticles

Abstract

Recently researchers have shown that water splitting occurs in 6 nm particles of Co-O, an effect not seen in the pure crystal, indicating that the band shift in these particles is probably due in part to surface modification. Others have shown that band edges in metal oxide crystals can be shifted up by induced dipoles on the surface. These are created by attaching polar molecules or passive ligands. Here we present a tight binding model that predicts that the observed band shift in Co-O is caused by the formation of local dipole moments, which result from dangling bonds on a distorted surface coupled to attached water molecules. Holding the bond distances fixed, we show that this effect occurs at a variety of bond angles. We show that the most probable angle is [Formula: see text], implying that this technique can be applied to the study of amorphous surfaces.