Effect of oxygen impurities on properties of the ternary superconductor SnMo6S8: 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 SnMo6S8, 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 Mössbauer isomer shift and quadrupole splitting values of Sn119 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 [Mo6S8]2- cluster was also studied. The results suggest that oxygen doping does not alter significantly the electronic structure of SnMo6S8.