Journal
CHEMISTRY OF MATERIALS
Volume 32, Issue 17, Pages 7404-7412Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.chemmater.0c02342
Keywords
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Funding
- UTA Startup funds
- Sigma Xi [G20191001100810061]
- National Science Foundation [DMR 1627197]
- Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC0205CH11231]
- DOE Office of Science [DE-SC0012704]
- Advanced Light Source (ALS) doctoral fellowship in residence
- Bates College Startup funds
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]
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Stereochemically active lone pairs of electrons play an important role in a diverse range of physical phenomena in many materials, ranging from semiconducting halide perovskites to thermochromic inorganic-organic hybrids. In this paper, we demonstrate the importance of the 6s(2) lone pair of Pb on the reversible thermochromic transition in the mixed-anion inorganic compound, PbVO3Cl. This 6s(2) stereochemically active lone pair results in subtle structural distortions upon heating while maintaining its overall orthorhombic structure. These distortions result in competing interactions with the Pb 6s(2) lone pair and ultimately, a pronounced change between yellow and red at similar to 200 degrees C. X-ray diffraction analyses of PbVO3Cl demonstrate two-dimensional features in contrast to the three-dimensional network in isostructural BaVO3Cl. X-ray and neutron pair distribution function experiments reveal that Pb-O interatomic distances decrease upon heating, while Pb-CI distances are only affected by thermal motion. X-ray photoelectron spectroscopy measurements provide experimental evidence of the presence of the 6s(2) lone pair at the valence band maximum, which are corroborated by first-principles calculations. The results demonstrate a broadly generalizable mechanism for using repulsions between lone-pair electrons of p-block cations to drive discontinuous changes of local symmetry and electronic structure.
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