10.1021/acs.inorgchem.9b01846.s001 Josie E. Auckett Josie E. Auckett Wai Tung Lee Wai Tung Lee Kirrily C. Rule Kirrily C. Rule Alexey Bosak Alexey Bosak Chris D. Ling Chris D. Ling Order, Disorder, and Dynamics in Brownmillerite Sr<sub>2</sub>Fe<sub>2</sub>O<sub>5</sub> American Chemical Society 2019 room-temperature structure Brownmillerite Sr 2 Fe 2 O 5 Sr 2 Fe 2 O 5 electron diffraction data brownmillerite-type Sr 2 Fe 2 O 5 satellite reflections neutron diffraction diffraction images X-ray length scales tetrahedral chain disagreements concern b axis FeO 4 tetrahedral chains oxide ion transport oxide-ionic conductivity powder samples 2019-08-23 12:09:24 Journal contribution https://acs.figshare.com/articles/journal_contribution/Order_Disorder_and_Dynamics_in_Brownmillerite_Sr_sub_2_sub_Fe_sub_2_sub_O_sub_5_sub_/9725030 The room-temperature structure of brownmillerite-type Sr<sub>2</sub>Fe<sub>2</sub>O<sub>5</sub> remains controversial, despite numerous published crystallographic studies utilizing X-ray, neutron, and electron diffraction data collected on single-crystalline and powder samples. The main disagreements concern the ordering of twisted FeO<sub>4</sub> tetrahedral chains within and between the layers stacked along the <i>b</i> axis, and the impact of this ordering on oxide-ionic conductivity. Here, we present new data along with a reinterpretation of previously published diffraction images, including the reassignment of satellite reflections, which harmonize the results of past studies in a unified description of tetrahedral chain ordering in Sr<sub>2</sub>Fe<sub>2</sub>O<sub>5</sub> at length scales relevant to X-ray and neutron diffraction. Implications for the prevailing model of oxide ion transport in this material are also discussed.