An ab initio characterization of the electronic structure of LaCo x Fe 1- x O 3 for x  ≤ 0.5

Solid oxide fuel cells are an important class of energy conversion devices in the search to replace fossil fuels. Their electrodes’ materials mostly belong to the perovskite family, which in their versatile composition are numerous; here we focus on the perovskite LaCoxFe1−xO3 and examine its electronic structure for x ≤ 0.5 using density functional theory with a plane wave basis and pseudopotentials. The resulting lattice parameters show good agreement with experiment, and the Mulliken and Bader charges show that iron and cobalt mostly remain as Fe3+ and Co3+ throughout an increasing Co:Fe ratio. The charge and spin magnitudes of oxygen ions is determined by their local, cation neighbors with the largest charge and spin magnitudes found on oxygen ions sandwiched between two Fe ions. Density of states and partial density of states analyses reveal that increasing the ratio of Co to Fe in oxygen stoichiometric materials decreases their relative, semi‐conducting nature toward insulating, by virtue of the decrease in the number of (conducting) O–Fe–O bonds and the increase in (insulating) O–Co–O bonds. The appearance of an intermediate spin state of Co and examination of its PDOS confirms the hypothesis that Co–O, d–p hybridization is a necessary factor for its occurrence