Comparative study of the electronic structure of alkaline-earth borides (MeB2; Me=Mg, Al, Zr, Nb, and Ta) and their normal-state conductivity

y means of density functional theory the electronic structure of the MgB2 superconductor was characterized and compared with that of the related iso-structural systems: AlB2, ZrB2, A NbB2, and TaB2. Using the full potential-linearized augmented plane wave (FP-LAPW) A method and the generalized gradient approximation, the electronic density distribution, density of states, and band structures were obtained for these compounds. The electrical conductivity, which cannot be easily measured in the c-direction, was calculated, in the relaxation time approximation using band structure results. It was found that the two-dimensional (2D) crystal structure character of these metallic diborides is also reflected in the electronic charge distribution. This 2D pattern is not reproduced in the electrical conductivity as it is, for instance, in the superconductor high Tc cuprates. The calculations indicate a bulk, yet anisotropic, conductivity for all these compounds.