Electronic bandstructures on 5d-transition metal pyrochlore: Cd2Re2O7 and Cd2Os2O7

The electronic bandstructure calculations for Cd₂Re₂O₇ and Cd₂Os₂O₇ are performed by using an FLAPW method based on the local density approximation, where the spin–orbit interactions are taken into account. It is found that the spin–orbit interaction changes significantly Re/Os-5d (t_2g) band dispersion situated near the Fermi level. Cd₂Re₂O₇ is a semi-metal, the Fermi level is located just in the valley, the specific heat coefficient is calculated as 2.7 mJ/K² mol Re and the carrier number is 0.039/cell in each hole and electron. The Re/Os-5d bands hybridize well with the O-p bands so that the Re/Os-5d component significantly appears even in the bottom of the wide O-p bands. Therefore, it is important to consider Re-5d O-p hybridization to investigate the physical properties of these compounds.