The Jahn-Teller Distortion at High Pressure: The Case of Copper Difluoride
AbstractThe opposing effects of high pressure (in the GPa range) and the Jahn-Teller distortion led to many intriguing phenomena which are still not well understood. Here we report a combined experimental-theoretical study on the high-pressure behavior of an archetypical Jahn-Teller system, copper difluoride (CuF2). At ambient conditions this compound adopts a distorted rutile structure of P21/c symmetry. Raman scattering measurements performed up to 29 GPa indicate that CuF2 undergoes a phase transition at 9 GPa. We assign the novel high-pressure phase to a distorted fluorite structure of Pbca symmetry, iso-structural with the ambient-pressure structure of AgF2. Density functional theory calculations indicate that the Pbca structure should transform to a non-centrosymmetric Pca21 polymorph above 30 GPa, which, in turn, should be replaced by a cotunnite phase (Pnma symmetry) at 72 GPa. The elongated octahedral coordination of the Cu2+ cation persists up to the Pca21–Pnma transition upon which it is replaced by a capped trigonal prism geometry, still bearing signs of a Jahn-Teller distortion. The high-pressure phase transitions of CuF2 resembles those found for difluorides of transition metals of similar radius (MgF2, ZnF2, CoF2), although with a much wider stability range of the fluorite-type structures, and lower dimensionality of the high-pressure polymorphs. Our calculations indicate no region of stability of a nanotubular polymorph observed for the related AgF2 system. View Full-Text
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Kurzydłowski, D. The Jahn-Teller Distortion at High Pressure: The Case of Copper Difluoride. Crystals 2018, 8, 140.
Kurzydłowski D. The Jahn-Teller Distortion at High Pressure: The Case of Copper Difluoride. Crystals. 2018; 8(3):140.Chicago/Turabian Style
Kurzydłowski, Dominik. 2018. "The Jahn-Teller Distortion at High Pressure: The Case of Copper Difluoride." Crystals 8, no. 3: 140.
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