Structure of CoO(001) surface from DFT + U calculations

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.