DFT+U Study of the electronic, magnetic and mechanical properties of Co, CoO, and Co3O4

Cobalt nanoparticles play an important role as a catalyst in the Fischer-Tropsch synthesis. During the reaction process, cobalt nanoparticles can become oxidised leading to the formation of two phases: CoO rock-salt and Co3O4 cubic spinel. It is therefore important to develop a fundamental description, at the atomic scale, of cobalt and its oxide phases which we have done here using density functional theory with the Dudarev approach to account for the on-site Coulomb interactions (DFT+U). We have explored different Ueff values, ranging from 0 to 5 eV, and found that Ueff = 3.0 eV describes most appropriately the mechanical properties, as well as the electronic and magnetic structures of Co, CoO, and Co3O4. The data described here are: 1- Calculated lattice parameters (c/a) for Co and (a) for the cubic cells of CoO and Co3O4 for different U values. 2- The calculated bulk modulus for different U values for Co, CoO, and Co3O4. 3- The magnetic moment per Co atom and band gap as a function of the U parameter for Co, CoO, and Co3O4. 4- The percent error of the unit cell, bulk modulus, magnetic moment, and band gap, as a function of the U parameter for Co, CoO, and Co3O4 5- The Electronic density of states (DOS) of Co, CoO, and Co3O4 6- The elastic constants (in GPa) of the three materials Co, CoO and Co3O4