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arXiv · 1405.5992

Superionicity and Polymorphism in Calcium Fluoride at High Pressure

Claudio Cazorla·Daniel Errandonea
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Abstract

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.

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Claudio Cazorla, Daniel Errandonea. 2014-09-18. Superionicity and Polymorphism in Calcium Fluoride at High Pressure. https://doi.org/10.1103/physrevlett.113.235902

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