Adsorption of the first row of transition metals on the perfect and defective MgO(1 0 0) surface

We present DFT calculations for adsorption of the first row of transition metal atoms on a MgO(1 0 0) surface and on a surface exhibiting F s 0 defects. Some atoms exhibit a high adsorption energy on the defect (e.g. Co, Ni and Cu), but others (Ca, Sc) rather adsorb on a clean surface and another set is indifferent to the presence of defect. The adsorption becomes energetically unfavorable when the σ anti-bonding orbitals become populated; this is worse on a defective surface than on a terrace. The π back-donation to the surface contributes to favor the adsorption on the F s 0 center.