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arXiv · 1912.01850

High-pressure phase transitions of zinc difluoride up to 55 GPa

Dominik Kurzydłowski·Anna Oleksiak·Sharad Babu Pillai·Prafulla K. Jha
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Abstract

Studying the effect of high pressure (exceeding 10 kbar) on the structure of solids allows to gain deeper insight in the mechanism governing crystal structure stability. Here we report a study on the high-pressure behaviour of zinc difluoride (ZnF2) - an archetypical ionic compound which at ambient pressure adopts the rutile (TiO2) structure. Previous investigations, limited to a pressure of 15 GPa, revealed that this compound undergoes two pressure-induced phase transitions: TiO2 - CaCl2 at 4.5 GPa, and CaCl2 - HP-PdF2 at 10 GPa. Within this joint experimental-theoretical study we extend the room temperature phase diagram of ZnF2 up to 55 GPa. By means of Raman spectroscopy measurements we identify two new phase transitions: HP-PdF2 - HP1-AgF2 at 30 GPa and HP1 AgF2 - PbCl2 at 44 GPa. These results are confirmed by Density Functional Theory calculations which indicate that in the HP1-AgF2 polymorph the coordination sphere of Zn2+ undergoes drastic changes upon compression. Our results point to important differences in the high-pressure behaviour of ZnF2 and MgF2, despite the fact that both compounds contain cations of similar size. We also argue that the HP1-AgF2 structure, previously observed only for AgF2, might be observed at large compression in other AB2 compounds.

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Dominik Kurzydłowski, Anna Oleksiak, Sharad Babu Pillai, Prafulla K. Jha. 2019-12-04. High-pressure phase transitions of zinc difluoride up to 55 GPa. https://doi.org/10.1021/acs.inorgchem.9b03553

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