Dynamic Stereochemical Activity of the Sn2+ Lone Pair in Perovskite CsSnBr3

Douglas H. Fabini, Geneva Laurita, Jonathon S. Bechtel, Constantinos C. Stoumpos, Hayden A. Evans, Athanassios G. Kontos, Yannis S. Raptis, Polycarpos Falaras, Anton Van Der Ven, Mercouri G. Kanatzidis, Ram Seshadri

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Abstract

Stable s2 lone pair electrons on heavy main-group elements in their lower oxidation states drive a range of important phenomena, such as the emergence of polar ground states in some ferroic materials. Here we study the perovskite halide CsSnBr3 as an embodiment of the broader materials class. We show that lone pair stereochemical activity due to the Sn2+ s2 lone pair causes a crystallographically hidden, locally distorted state to appear upon warming, a phenomenon previously referred to as emphanisis. The synchrotron X-ray pair distribution function acquired between 300 and 420 K reveals emerging asymmetry in the nearest-neighbor Sn-Br correlations, consistent with dynamic Sn2+ off-centering, despite there being no evidence of any deviation from the average cubic structure. Computation based on density functional theory supports the finding of a lattice instability associated with dynamic off-centering of Sn2+ in its coordination environment. Photoluminescence measurements reveal an unusual blue-shift with increasing temperature, closely linked to the structural evolution. At low temperatures, the structures reflect the influence of octahedral rotation. A continuous transition from an orthorhombic structure (Pnma, no. 62) to a tetragonal structure (P4/mbm, no. 127) is found around 250 K, with a final, first-order transformation at 286 K to the cubic structure (Pm3-m, no. 221).

Original languageEnglish
Pages (from-to)11820-11832
Number of pages13
JournalJournal of the American Chemical Society
Volume138
Issue number36
DOIs
Publication statusPublished - Sep 14 2016

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Fabini, D. H., Laurita, G., Bechtel, J. S., Stoumpos, C. C., Evans, H. A., Kontos, A. G., Raptis, Y. S., Falaras, P., Van Der Ven, A., Kanatzidis, M. G., & Seshadri, R. (2016). Dynamic Stereochemical Activity of the Sn2+ Lone Pair in Perovskite CsSnBr3. Journal of the American Chemical Society, 138(36), 11820-11832. https://doi.org/10.1021/jacs.6b06287