ORBITAL POLARIZATION IN LIVO2 AND NATIO2

We present a band structure study of orbital polarization and ordering in the two-dimensional triangular-lattice transition metal compounds LiVO2 and NaTiO2. It is found that while in NaTiO2 the degeneracy of t a, orbitals is lifted due to the trigonal symmetry of the crystal and the strong on-site Coulomb interaction, in LiVO2 orbital degeneracy re mains and orbital ordering corresponding to the trimerization of the t wo-dimensional lattice develops.