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RESEARCH PRODUCT
Superionicity and polymorphism in calcium fluoride at high pressure.
Claudio CazorlaDaniel Errandoneasubject
Condensed Matter - Materials ScienceMaterials scienceCondensed matter physicsPhononGeneral Physics and Astronomychemistry.chemical_elementMaterials Science (cond-mat.mtrl-sci)FOS: Physical sciencesConductivityFluoritePolymorphism (materials science)chemistryHigh pressureFluorineSofteningMonoclinic crystal systemdescription
We present a combined experimental and computational first-principles study of the superionic and structural properties of CaF2 at high P-T conditions. We observe an anomalous superionic behavior in the low-P fluorite phase that consists in a decrease of the normal-> superionic critical temperature with compression. This unexpected effect can be explained in terms of a P-induced softening of a zone-boundary $X$ phonon which involves exclusively fluorine displacements. Also we find that superionic conductivity is absent in the high-P cotunnite phase. Instead, superionicity develops in a new low-symmetry high-T phase that we identify as monoclinic (space group P2_1/c). We discuss the possibility of observing these intriguing phenomena in related isomorphic materials.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2014-05-23 | Physical review letters |