Abstract
We present a combination of neutron powder-diffraction measurements demonstrating negative linear compressibility and irregular thermal expansion in 7Li2CO3. 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.
| Original language | English |
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| Pages (from-to) | 25335-25344 |
| Number of pages | 10 |
| Journal | Journal of Materials Chemistry A |
| Volume | 13 |
| Issue number | 31 |
| DOIs | |
| State | Published - Aug 5 2025 |
Funding
The authors acknowledge the Science and Technology Facilities Council for providing neutron beamtime on the PEARL instrument at the ISIS Neutron and Muon Source,56 and are grateful to Claire Talbott and Adam Sears (Pressure and Furnace Section, ISIS Neutron and Muon Source) for their assistance in running the high-temperature measurements. We also thank the Materials Characterisation Laboratory at the ISIS Neutron and Muon Source for access to the single-crystal XRD facilities. We acknowledge the computing resources provided the STFC Scientific Computing Department's SCARF cluster. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.57 The beam time was allocated to the SNAP instrument on proposal number IPTS-28913 and IPTS-34329. This research used resources of the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.