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 orbita l compositions of the partially filled bands were analyzed. The partia lly-filled bands are mainly composed of the La z(2) and x(2) - y(2) or bitals, but their relative contributions depend strongly on the wave v ectors. Thus the Fermi surface is strongly warped so that LaI2 does no t possess an electronic instability typically expected for a system wi th a nested Fermi surface. The absence of a metal atom clustering in L aI2 was discussed from the viewpoints of the strain and the preferenti al direction of metal-metal bonding of the square lattice. The Fermi s urface has the shape of a warped-square cylinder running along the Gam ma --> Z direction (i.e., perpendicular to the layer), and the cross-s ectional area (taken perpendicular to Gamma --> Z) oscillates between two slightly different values, so that the magnetoresistance of LaI2 i s predicted to exhibit angle-dependent oscillations.