It was recalled that, using density-functional theoretical calculations, it had been reported that formal Fe3+ ions resided at the square-pyramidal site and Fe4+ ions in the octahedral site in Sr4Fe4O11. Based upon the interpretation of experimental structural and Mössbauer data from the literature, Adler had concluded that these

oxidation states to Fe in the square-pyramidal and octahedral environments in Sr4Fe4O11. From a critical examination of the structure data for Sr4Fe4O11 and related oxides with Fe in different oxidation states and theoretically simulated Mössbauer parameters (hyperfine field, isomer shift, and quadrupole splitting), it was shown here that information on charges residing on the different constituents could not be derived directly from either experimental structure or Mössbauer data. From additional analyses of the chemical bonding on the basis of charge density, charge transfer, electron localization function, crystal orbital Hamilton population, Born effective charge, and partial density of states, a previous assignment of formal Fe3+ and Fe4+ to the square-pyramidal and octahedral sites, respectively, in Sr4Fe4O11 was substantiated.

Reply to “Comment on `Spin- and Charge-Ordering in Oxygen-Vacancy-Ordered Mixed-Valence Sr4Fe4O11'”. P.Ravindran, R.Vidya, H.Fjellvåg, A.Kjekshus: Physical Review B, 2008, 77[13], 136402 (4pp)