Electronic-structure study ofRuS2

We report an electrolyte-electroreflectance (EER) study of a ${\mathrm{RuS}}_2$ single crystal in the energy range 1.9–5.1 eV. The EER spectrum exhibits sharp structure in the vicinity of interband transitions. Transition energies are determined accurately. Photocurrent versus wavelength measurements show an indirect band gap of 1.38 eV. Combining the results of the EER and photocurrent measurements, we construct a possible energy-band structure. It is proposed that ${\mathrm{RuS}}_2$ has a completely filled 4d $t_{2g}$ band occupied by six electrons in the low-spin configuration, separated from empty S 3p ${\sigma }^{\mathrm{*}}$ and Ru 4d $e_g^{\mathrm{*}}$ bands, and the bottom of the conduction band corresponds to the S 3p ${\sigma }^{\mathrm{*}}$ antibonding states, in agreement with the calculation of Holzwarth et al., but contradicting the assumption of several other authors.