Reply to “Comment on ‘Spin- and charge-ordering in oxygen-vacancy-ordered mixed-valenceSr4Fe4O11’ ”

Abstract

Recently, using density-functional theoretical calculations, we have reported [Phys. Rev. B 74, 054422 (2006)] that formal ${\mathrm{Fe}}^{3+}$ ions reside at the square-pyramidal site and ${\mathrm{Fe}}^{4+}$ ions in the octahedral site in ${\mathrm{Sr}}_{4}{\mathrm{Fe}}_{4}{\mathrm{O}}_{11}$. Based on the interpretation of experimental structural and M\ossbauer data from the literature, Adler concludes that our previous first-principles results disagree with experiments on the assignment of oxidation states to Fe in the square-pyramidal and octahedral environments in ${\mathrm{Sr}}_{4}{\mathrm{Fe}}_{4}{\mathrm{O}}_{11}$. From a critical examination of the structure data for ${\mathrm{Sr}}_{4}{\mathrm{Fe}}_{4}{\mathrm{O}}_{11}$ and related oxides with Fe in different oxidation states and theoretically simulated M\ossbauer parameters (hyperfine field, isomer shift, and quadrupole splitting), here we show that information on charges residing on the different constituents cannot be directly derived either from experimental structure or M\ossbauer 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, we substantiate our previous assignment of formal ${\mathrm{Fe}}^{3+}$ and ${\mathrm{Fe}}^{4+}$ to the square-pyramidal and octahedral sites, respectively, in ${\mathrm{Sr}}_{4}{\mathrm{Fe}}_{4}{\mathrm{O}}_{11}$.