ELECTRONIC STRUCTURE AND MAGNETISM IN TRANSITION METAL DIBORIDES

摘要

The first type of bonds is developed in boron planes perpendicular to the crystal ternary axis and give hexagonal nets similar to graphite (sp2 hybridization). The second type occurs in close-packed hexagonal metal planes, and probably also between metal atoms arranged on top of each other. In a typical compound (e.g. TiB2) the parameter a has a value which fits in both with the covalency radius of boron (B-B bonds) and the metallic radius of titanium (Ti-Ti bonds in basal plane).nThe occurrence of direct metal bonds must involve, here as with other transition metal compounds, the occurrence at the Ferni level of a high density, d-character bond. The fact that the same crystallographic structure is preserved in the first transition series from scandium to manganese provides a good basis for the study of this type of bonds.