The orbital interaction of adsorbed CO on NiO (0 0 1;1 1 1) surface: A periodic density functional theory study

The DOS structures of NiO (0 0 1;1 1 1) surfaces and CO adsorption on these surfaces have been studied with spin-unrestricted and periodic DFT (B3LYP) methods. On the basis of the analysis of orbital interaction on DOSs, the bonding properties of surface atomic orbitals have also been interpreted. It is found that CO adsorption on (0 0 1) and (1 1 1) surfaces have different mechanisms and adsorption energies. A four-electron σ orbital interaction is produced when CO is adsorbed on NiO (1 1 1), CO adsorbption on NiO (1 1 1) surface is obviously stronger than that on surface (0 0 1). It is easy for the clean NiO (1 1 1) surface to reconstruct to (2 × 2) structure, but the surface covered by CO does not undergo such a reconstruction.