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 MndopedLaCoO3 nano scale layers in the rhombohedral phase have been investigated inthis paper. First, we employed the local density approximation (LDA) method with thegeneralized gradient approximation (GGA) under density functional theory (DFT). Thecalculated results did not show an appropriate consistency with experimental values.Knowing the presence of 3d orbitals in Co atom, to taking account the stronglocalization of electrons, we used the local spin density approximation plus a Hubbardliketerm (LSDA+U). Calculations were performed using different U values at lowtemperature and the obtained results showed high consistency with the experimentalvaluesand the optimum results were obtained for U=1.The calculated band structuresalong with the partial densities of states (PDOS) shows the nonmagnetic nature ofLaCoO3 at low temperatures. Also, adding Mn has a significant effect on the electronicproperties of LaCoO3. It was revealed that Mn changes the nonmagnetic characteristicof the compound to the magnetic feature.The bandgap values for spin up (SU) and spindown (SD) states have been calculated 0.9 eV and 1.2 eV, respectively and both stateshave direct bandgap.