Electronic structure of ${\mathrm{RuO}}_2$, ${\mathrm{OsO}}_2$, and ${\mathrm{IrO}}_2$

The Slater-Koster linear-combination-of-atomic-orbitals (LCAO) interpolation method is applied to fit the results of nonrelativistic augmented-plane-wave (APW) calculations at symmetry points in the Brillouin zone for several metallic transition-metal dioxides with the rutile structure, namely, ${\mathrm{RuO}}_2$, ${\mathrm{OsO}}_2$, and ${\mathrm{IrO}}_2$. This LCAO model, which involves Bloch sums formed from the oxygen $2s-2p$ and metal-atom $d$ orbitals, fits 92 APW energy eigenvalues with a 5-mRy rms error by means of 37 adjustable two-center parameters. The results of this APW-LCAO model are applied to determine the band profiles, density of states, and Fermi surfaces for each of these compounds. It is found that the Fermi-surface topology of these materials is altered significantly by the effects of spin-orbit coupling involving the metal-atom $d$ orbitals. These effects are included in this APW-LCAO band model by means of an additional parameter, the spin-orbit parameter ${\xi }_d$. The resulting Fermi surfaces are in good qualitative agreement with those inferred from magnetothermal-oscillation data by Graebner et al.