Structure of CoO(001) surface from DFTÂ +Â U calculations

•CoO(001) surface atoms do not exhibit the same relaxation.•CoO(001) surface shows some rumplings.•This surface has very low surface energy.•In the [001] direction, CoO of few layers contains Multiple Quantum Wells.

We report on the structure of CoO(001) surface. For DFT + U calculations, in order to reach the ground state, the parameter U is obtained by a self-consistent procedure based on the linear-response approach. After confirmation with respect to the experimental bandgap, the calculated parameter U is 3.7 eV. We show that this value is suitable for a good description of CoO electronic and magnetic properties. Contrary to most surfaces, CoO(001) topmost layers relax outwards with the oxygen ions relaxation height greater than that of cobalt ions, leading the surface to exhibit a small rumpling. This surface appears to be catalytically very favorable due to its low surface energy of 0.8 J/m2. It is also shown that this material exhibits Multiple Quantum-Well behavior and thus could be a good candidate for optoelectronic applications.