H. F. Pen | Searcharxiv

arXiv1997

Orbital polarization in LiVO_2 and NaTiO_2

We present a band structure study of orbital polarization and ordering in the two-dimensional triangular lattice transition metal compounds LiVO_2 and NaTiO_2. It is found that while in NaTiO_2 the degeneracy of t_{2g} orbitals is lifted due to the trigonal symmetry of the crystal and the strong on cite Coulomb interaction, in LiVO_2 orbital degeneracy remains and orbital ordering corresponding to the trimerization of the two-dimensional lattice develops.

cond-mat.str-el↗

arXiv1997

Kondo--lattice-like effects of hydrogen in transition metals

We discuss the possibility of a Kondo like effect associated with H in metals resulting from the strong dependence of the H1s orbital radius on the occupation number. We demonstrate that such a strong breathing property of the orbital radius, which translates directly into a strong occupation dependent hopping, results in the formation of local singlet-like bound states involving one electron on H and one on the surrounding metal orbitals. We also show that already at a mean field level an occupation dependent hopping integral leads to a substantial potential energy correction on hydrogen, and that the failure of LDA to incorporate this correction is probably responsible for the incorrect prediction of a metallic ground state for the YH3 switchable mirror compounds.

cond-mat.str-el↗