Ab-initio LSDA Study of the Electronic States of Nano Scale Layered LaCoO3/Mn Compound: Hubbard Parameter Optimization

Influences of spin polarization on the electronic traits of undoped and Mndoped LaCoO3 nano scale layers in the rhombohedral phase have been investigated in this paper. First, we employed the local density approximation (LDA) method with the generalized gradient approximation (GGA) under density functional theory (DFT). The calculated results did not show an appropriate consistency with experimental values. Knowing the presence of 3d orbitals in Co atom, to taking account the strong localization of electrons, we used the local spin density approximation plus a Hubbardlike term (LSDA+U). Calculations were performed using different U values at low temperature and the obtained results showed high consistency with the experimental valuesand the optimum results were obtained for U=1.The calculated band structures along with the partial densities of states (PDOS) shows the nonmagnetic nature of LaCoO3 at low temperatures. Also, adding Mn has a significant effect on the electronic properties of LaCoO3. It was revealed that Mn changes the nonmagnetic characteristic of the compound to the magnetic feature.The bandgap values for spin up (SU) and spin down (SD) states have been calculated 0.9 eV and 1.2 eV, respectively and both states have direct bandgap.