The origin of the insulating ground states and the charge disproportionation in the two Fe-based perovskite oxides, viz., $\mathrm{Ca}\mathrm{Fe}{\mathrm{O}}_3$ and ${\mathrm{La}}_{1∕3}{\mathrm{Sr}}_{2∕3}\mathrm{Fe}{\mathrm{O}}_3$, are examined from ab initio electronic structure calculations based on the density-functional methods. We find that correlation effects beyond the local density approximation as well as lattice distortions are necessary to describe the electronic properties of both compounds. It is the intricate interplay between lattice distortion and correlation effect that describes both the charge disproportionation and insulating ground state within the band theory, as is observed in these compounds.

• Received 10 March 2005

DOI:https://doi.org/10.1103/PhysRevB.72.045143