Clemens Oliver, Gröting Melanie, Witte Ralf, Perez-Mato J Manuel, Loho Christoph, Berry Frank J, Kruk Robert, Knight Kevin S, Wright Adrian J, Hahn Horst, Slater Peter R
Joint Research Laboratory Nanomaterials and §Fachgebiet Materialmodellierung, Technische Universität Darmstadt , Jovanka-Bontschits-Straße 2, 64287 Darmstadt, Germany.
Inorg Chem. 2014 Jun 16;53(12):5911-21. doi: 10.1021/ic402988y. Epub 2014 Jun 5.
We report here on the characterization of the vacancy-ordered perovskite-type structure of BaFeO2.5 by means of combined Rietveld analysis of powder X-ray and neutron diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c [a = 6.9753(1) Å, b = 11.7281(2) Å, c = 23.4507(4) Å, β = 98.813(1)°, and Z = 28] containing seven crystallographically different iron atoms. The coordination scheme is determined to be Ba7(FeO4/2)1(FeO3/2O1/1)3(FeO5/2)2(FeO6/2)1 = Ba7Fe([6])1Fe([5])2Fe([4])4O17.5 and is in agreement with the (57)Fe Mössbauer spectra and density functional theory based calculations. To our knowledge, the structure of BaFeO2.5 is the most complicated perovskite-type superstructure reported so far (largest primitive cell, number of ABX2.5 units per unit cell, and number of different crystallographic sites). The magnetic structure was determined from the powder neutron diffraction data and can be understood in terms of "G-type" antiferromagnetic ordering between connected iron-containing polyhedra, in agreement with field-sweep and zero-field-cooled/field-cooled measurements.
我们在此报告通过粉末X射线和中子衍射数据的联合Rietveld分析对BaFeO₂.₅的空位有序钙钛矿型结构的表征。该化合物结晶于单斜空间群P2(1)/c [a = 6.9753(1) Å, b = 11.7281(2) Å, c = 23.4507(4) Å, β = 98.813(1)°, 且Z = 28]，包含七个晶体学上不同的铁原子。配位方案确定为Ba₇(FeO₄/₂)₁(FeO₃/₂O₁/₁)₃(FeO₅/₂)₂(FeO₆/₂)₁ = Ba₇Fe([6])₁Fe([5])₂Fe([4])₄O₁₇.₅，并且与(⁵⁷)Fe穆斯堡尔谱和基于密度泛函理论的计算结果一致。据我们所知，BaFeO₂.₅的结构是迄今为止报道的最复杂的钙钛矿型超结构（最大的原胞、每个晶胞中ABX₂.₅单元的数量以及不同晶体学位点的数量）。磁结构由粉末中子衍射数据确定，并且可以通过相连的含铁多面体之间的“G型”反铁磁有序来理解，这与场扫描和零场冷却/场冷却测量结果一致。
