Using first-principles calculations based on density functional theory (DFT) we compare the generalized gradient approximation (GGA-PBE) with a screened hybrid functional by studying the electronic and optical properties of bulk LaAlO3 in the cubic and rhombohedral phases. We find that both atomic and electronic structures are accurately described by the hybrid functional. The hybrid functional not only corrects the band gap, when compared to GGA-PBE, it also shifts the unoccupied La 4f bands to higher energies with respect to the hybridized conduction-band minimum, composed of 83% La 4d, 5% La 4f, 6% O 2s, and 6% O 2p states. We show that this shift is essential to accurately describe the complex dielectric function, in good agreement with experimental results. We conclude that the screened hybrid functional offers a reliable description of the position of empty f bands with respect to the valence- and conduction-band edges in LaAlO3.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics