Abstract
Elpasolite- and cryolite-type oxyfluorides can be regarded as superstructures of perovskite and exhibit structural diversity. While maintaining a similar structural topology with the prototype structures, changes in the size, electronegativity, and charge of cation and/or anion inevitably lead to structural evolution. Therefore, the nominal one-to-one relation suggested by a doubled formula of perovskite does not guarantee a simple 2-fold superstructure for many cases. Herein, the commensurately modulated perovskite-like K3TiOF5 was refined at 100 K from single-crystal X-ray diffraction data by using a pseudotetragonal subcell with lattice parameters of a = b = 6.066(2) Å and c = 8.628(2) Å. The length of the modulation vector was refined to 0.3a∗ + 0.1b∗ + 0.25c*. In the commensurate supercell of K3TiOF5, the B-site Ti4+ and K+ cations in [TiOF5]3- and [KOF5]6- octahedral units were found to be significantly displaced from the average atomic positions refined in the subcell. The displacements of the K+ cations are ±0.76 Å, and those for the Ti4+ cations are approximately ±0.13 Å. One- and two-dimensional solid-state 19F NMR measurements revealed two tightly clustered groups of resonances in a ratio of ca. 4:1, assigned to equatorial and axial fluorine, respectively, consistent with local [TiOF5]3- units. S/TEM results confirmed the average structure. Electronic structure calculations of the idealized I4mm subcell indicate the instability to a modulated structure arises from soft optical modes that is controlled by the octahedrally coordinated B-site potassium ions in the cryolite-type structure.
Original language | English (US) |
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Pages (from-to) | 18907-18916 |
Number of pages | 10 |
Journal | Journal of the American Chemical Society |
Volume | 143 |
Issue number | 45 |
DOIs | |
State | Published - Nov 17 2021 |
Funding
F.D., C.D.M. and M.L.N. were supported by funding from the National Science Foundation (DMR-1904701) for the single-crystal XRD work. NMR studies performed by K.J.G. were supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Theoretical and computational work of J.K.H. N.C., and J.M.R. were supported by NSF (DMR-1454688 and DMR-2011208). W.G. and P.S.H. thank the Welch Foundation (Grant E-1457) and the National Science Foundation (DMR-2002319) for support. Experimental synthesis and structure characterization by J.K.H., C.Z., K.R.P. J.M.R., and V.P.D. were supported by the National Science Foundation’s (NSF) MRSEC program (DMR-1720139) at the Materials Research Center of Northwestern University. The single-crystal X-ray data, NMR, and FT-IR measurements were acquired at Northwestern University′s Integrated Molecular Structure Education and Research Center (IMSERC) at Northwestern University, which is supported by grants from NSF-NSEC NSF-MRSEC, the KECK Foundation, the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), the State of Illinois and Northwestern University. This work made use of the J. B. Cohen X-ray Diffraction Facility supported by the MRSEC program of the National Science Foundation (DMR-1720139) at the Materials Research Center of Northwestern University. DFT calculations were performed on the high-performance computing facilities available at the Extreme Science and Engineering Discovery Environment (XSEDE), which was supported by NSF Grant ACI-1548562. F.D., C.D.M., and M.L.N. were supported by funding from the National Science Foundation (DMR-1904701) for the single-crystal XRD work. NMR studies performed by K.J.G. were supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Theoretical and computational work of J.K.H., N.C., and J.M.R. were supported by NSF (DMR-1454688 and DMR-2011208). W.G. and P.S.H. thank the Welch Foundation (Grant E-1457) and the National Science Foundation (DMR-2002319) for support. Experimental synthesis and structure characterization by J.K.H., C.Z., K.R.P., J.M.R., and V.P.D. were supported by the National Science Foundation’s (NSF) MRSEC program (DMR-1720139) at the Materials Research Center of Northwestern University. The single-crystal X-ray data, NMR, and FT-IR measurements were acquired at Northwestern University′s Integrated Molecular Structure Education and Research Center (IMSERC) at Northwestern University, which is supported by grants from NSF-NSEC, NSF-MRSEC, the KECK Foundation, the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), the State of Illinois, and Northwestern University. This work made use of the J. B. Cohen X-ray Diffraction Facility supported by the MRSEC program of the National Science Foundation (DMR-1720139) at the Materials Research Center of Northwestern University. DFT calculations were performed on the high-performance computing facilities available at the Extreme Science and Engineering Discovery Environment (XSEDE), which was supported by NSF Grant ACI-1548562.
ASJC Scopus subject areas
- Catalysis
- General Chemistry
- Biochemistry
- Colloid and Surface Chemistry
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CSD 2085578: Experimental Crystal Structure Determination
Ding, F. (Contributor), Charles, N. (Contributor), Harada, J. K. (Contributor), Malliakas, C. D. (Contributor), Zhang, C. (Contributor), Dos Reis, R. (Contributor), Griffith, K. J. (Contributor), Nisbet, M. L. (Contributor), Zhang, W. (Contributor), Halasyamani, P. S. (Contributor), Dravid, V. P. (Contributor), Rondinelli, J. M. (Contributor) & Poeppelmeier, K. R. (Contributor), FIZ Karlsruhe - Leibniz Institute for Information Infrastructure, 2021
DOI: 10.25505/fiz.icsd.cc2806q7, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.25505/fiz.icsd.cc2806q7&sid=DataCite
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