Simulation techniques were used to investigate the defect properties of this oxyfluoride superconductor. The observed La2CuO4-type structure of this material was correctly reproduced by the interatomic potential model that was used. Defect calculations indicated that the most favorable F interstitial position was located near to the ideal site, and was associated with a significant local relaxation; in accord with diffraction studies. The results confirmed that oxidation, which involved F incorporation at interstitial sites, was the most favorable process for introducing the holes that were necessary for superconductivity.

S.D’Arco, M.S.Islam: Physical Review B, 1997, 55[5], 3141-5