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Saura-Múzquiz M, Marlton FP, Mullens BG, Manjón-Sanz AM, Neuefeind JC, Everett M, Brand HEA, Mondal S, Vaitheeswaran G, Kennedy BJ. Understanding the Re-entrant Phase Transition in a Non-magnetic Scheelite. J Am Chem Soc 2022; 144:15612-15621. [PMID: 35994733 DOI: 10.1021/jacs.2c05620] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The stereochemical activity of lone pair electrons plays a central role in determining the structural and electronic properties of both chemically simple materials such as H2O, as well as more complex condensed phases such as photocatalysts or thermoelectrics. TlReO4 is a rare example of a non-magnetic material exhibiting a re-entrant phase transition and emphanitic behavior in the long-range structure. Here, we describe the role of the Tl+ 6s2 lone pair electrons in these unusual phase transitions and illustrate its tunability by chemical doping, which has broad implications for functional materials containing lone pair bearing cations. First-principles density functional calculations clearly show the contribution of the Tl+ 6s2 in the valence band region. Local structure analysis, via neutron total scattering, revealed that changes in the long-range structure of TlReO4 occur due to changes in the correlation length of the Tl+ lone pairs. This has a significant effect on the anion interactions, with long-range ordered lone pairs creating a more densely packed structure. This resulted in a trade-off between anionic repulsions and lone pair correlations that lead to symmetry lowering upon heating in the long-range structure, whereby lattice expansion was necessary for the Tl+ lone pairs to become highly correlated. Similarly, introducing lattice expansion through chemical pressure allowed long-range lone pair correlations to occur over a wider temperature range, demonstrating a method for tuning the energy landscape of lone pair containing functional materials.
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Affiliation(s)
- Matilde Saura-Múzquiz
- School of Chemistry, University of Sydney, F11, Sydney, New South Wales 2006, Australia
| | - Frederick P Marlton
- School of Chemistry, University of Sydney, F11, Sydney, New South Wales 2006, Australia
| | - Bryce G Mullens
- School of Chemistry, University of Sydney, F11, Sydney, New South Wales 2006, Australia
| | - Alicia María Manjón-Sanz
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Joerg C Neuefeind
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Michelle Everett
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Helen E A Brand
- Australian Synchrotron, Australian Nuclear Science and Technology Organisation, 800 Blackburn Road, Clayton, Victoria 3168, Australia
| | - Subrata Mondal
- Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad 500046, Telangana, India
| | - Ganapathy Vaitheeswaran
- School of Physics, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad 500046, Telangana, India
| | - Brendan J Kennedy
- School of Chemistry, University of Sydney, F11, Sydney, New South Wales 2006, Australia
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