Electronic Structure of LiMnO$_{2}$: A Comparative Study of the LSDA and LSDA+U methods

摘要

A first-principles electronic structure study of orthorhombic, monoclinic andrhombohedral LiMnO$_{2}$ has been carried out using the full-potentiallinearized augmented plane-wave method. The exchange and correlations have beentreated within the local spin-density approximation (LSDA) and the LSDA+Umethods. In the LSDA, the stable ground state is antiferromagnetic insulatorfor the orthorhombic and monoclinic structures but is ferromagnetic metal forthe rhombohedral structure. The LSDA+U, on the other hand, predicts the groundstate to be an antiferromagnetic insulator for all structures. We find thatstrong correlations change the density of states dramatically around the Fermilevel. The LSDA+U predicts the nature of band gap to be a mixture of chargetransfer and Mn $d \leftrightarrow d$ like excitations for orthorhombic andmonoclinic LiMnO$_{2}$ and Mott-insulator for rhombohedral LiMnO$_{2}$ inagreement with the available experimental results. The inclusion of U increasesthe magnetic moment on Mn and gives a value in better agreement withexperiment. However, Mn valency is not affected by the inclusion of U. We havealso calculated X-ray emission photoelectron spectra for the orthorhombic andmonoclinic LiMnO$_{2}$ by the LSDA and the LSDA+U methods. We find that LSDA+Ugives better agreement with the available experimental results.