ANALYSIS OF THE PARTIALLY-FILLED D-BLOCK BAND OF THE LAYERED METAL LAI2 AND PROBABLE CAUSE FOR THE ABSENCE OF STRUCTURAL INSTABILITY

The electronic band structure of the layered metal LaI2 was calculated by employing the extended Huckel tight binding method, and the orbital compositions of the partially filled bands were analyzed. The partially-filled bands are mainly composed of the La z(2) and x(2) - y(2) orbitals, but their relative contributions depend strongly on the wave vectors. Thus the Fermi surface is strongly warped so that LaI2 does not possess an electronic instability typically expected for a system with a nested Fermi surface. The absence of a metal atom clustering in LaI2 was discussed from the viewpoints of the strain and the preferential direction of metal-metal bonding of the square lattice. The Fermi surface has the shape of a warped-square cylinder running along the Gamma --> Z direction (i.e., perpendicular to the layer), and the cross-sectional area (taken perpendicular to Gamma --> Z) oscillates between two slightly different values, so that the magnetoresistance of LaI2 is predicted to exhibit angle-dependent oscillations.