Effect of oxygen impurities on properties of the ternary superconductorSnMo6S8: Extended x-ray-absorption fine-structure determination of bond distances and local-density cluster calculations

Electronic structure calculations were performed for clusters representing the Chevrel-phase ${\mathrm{SnMo}}_{6}$${\mathrm{S}}_{8}$, with and without oxygen doping. In order to obtain the local structure around the Sn atom, extended x-ray-absorption fine-structure (EXAFS) measurements were made with synchro- tron radiation. The interatomic distances obtained experimentally were used in the calculations. The effect of oxygen doping on the M\"ossbauer isomer shift and quadrupole splitting values of $^{119}\mathrm{Sn}$ was investigated theoretically and compared with reported experimental values. The effect of oxygen substitution on the density of states at the Fermi energy of the [${\mathrm{Mo}}_{6}$${\mathrm{S}}_{8}$${]}^{2\mathrm{\ensuremath{-}}}$ cluster was also studied. The results suggest that oxygen doping does not alter significantly the electronic structure of ${\mathrm{SnMo}}_{6}$${\mathrm{S}}_{8}$.