Towards understanding the special stability of SrCoO2.5 and HSrCoO2.5
Abstract
Reversible hydrogen incorporation was recently attested [Lu et al., Nature (London) 546, 124 (2017), 10.1038/nature22389] in SrCoO2.5, the brownmillerite phase (BM) of strontium cobalt oxide (SCO), opening new avenues in catalysis and energy applications. However, existing theoretical studies of BM-SCO are insufficient, and that of HSrCoO2.5, the newly reported hydrogenated SCO (H-SCO) phase, is especially scarce. In this work, we demonstrate how the electron-counting model can be used in understanding the phases, particularly in explaining the stability of the oxygen-vacancy channels, and in examining the Co valance problem. Using density-functional theoretical methods, we analyze the crystalline, electronic, and magnetic structures of BM- and H-SCO. Based on our structure search, we discovered stable phases with large band gaps (>1 eV) for both BM-SCO and H-SCO, agreeing better with experiments on the electronic structures. Our calculations also indicate limited charge transfer from H to O, which may explain the special stability of the H-SCO phase and the reversibility of H incorporation observed in experiments. Contrary to the initial study, our calculations also suggest intrinsic antiferromagnetism of H-SCO, showing how the measured ferromagnetism has possible roots in hole doping.
- Publication:
-
Physical Review Materials
- Pub Date:
- February 2019
- DOI:
- 10.1103/PhysRevMaterials.3.024603
- arXiv:
- arXiv:1806.03917
- Bibcode:
- 2019PhRvM...3b4603T
- Keywords:
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- Condensed Matter - Materials Science
- E-Print:
- 9 pages, 10 figures, 4 tables + supplemental material