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DOE OSTI · 2575301

Negative linear compressibility and complex phase behaviour in 7 Li 2 CO 3

Ridley, Christopher J. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)] (ORCID:0000000230609656)·Orlandi, Fabio [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)] (ORCID:000000016333521X)·Bull, Craig L. [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom); Univ. of Edinburgh, Scotland (United Kingdom)] (ORCID:0000000251706674)·Funnell, Nicholas P. [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)] (ORCID:000000016280036X)·Hinton, Jasmine K. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:000000034417462X)·Perry, Robin S. [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom); Univ. College London (United Kingdom)]·Hull, Stephen [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)] (ORCID:0000000160783463)·Wurr, Rebecca [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom); King's College London (United Kingdom)] (ORCID:0000000271275859)
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Abstract

We present a combination of neutron powder-diffraction measurements demonstrating negative linear compressibility and irregular thermal expansion in 7 Li 2 CO 3 . This is shown to be due to an interplay between the tilting of the rigid carbonate group and the shear strain in the unit cell, which leads to a first-order transition from monoclinic to hexagonal symmetry. The phase evolution is shown to be highly sensitive to the level of hydrostaticity in the sample. Under hydrostatic conditions, the sample begins transformation at 8.5 GPa leading to a change from tetrahedral to octahedral Li coordination. Symmetry adapted basis mode analysis, combined with density functional theoretical (DFT) calculations and Raman spectroscopy, is used to show that this transition is reverse proper ferroelastic in nature.

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Ridley, Christopher J. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)] (ORCID:0000000230609656), Orlandi, Fabio [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)] (ORCID:000000016333521X), Bull, Craig L. [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom); Univ. of Edinburgh, Scotland (United Kingdom)] (ORCID:0000000251706674), Funnell, Nicholas P. [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)] (ORCID:000000016280036X), Hinton, Jasmine K. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:000000034417462X), Perry, Robin S. [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom); Univ. College London (United Kingdom)], Hull, Stephen [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)] (ORCID:0000000160783463), Wurr, Rebecca [Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom); King's College London (United Kingdom)] (ORCID:0000000271275859). 2025-05-14. Negative linear compressibility and complex phase behaviour in 7 Li 2 CO 3. https://doi.org/10.1039/d5ta02325d

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