Volume and pressure dependences of the electronic, vibrational, and crystal structures of C s2CoC l4: Identification of a pressure-induced piezochromic phase at high pressure

L. Nataf, F. Aguado, I. Hernández, R. Valiente, J. González, M. N. Sanz-Ortiz, H. Wilhelm, A. P. Jephcoat, F. Baudelet, F. Rodríguez

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Abstract

This work investigates the high-pressure structure of Cs2CoCl4 and how it affects the electronic and vibrational properties using optical absorption, Raman spectroscopy, x-ray diffraction, and x-ray absorption in the 0-15 GPa range. In particular, we focus on the electronic and local structures of Co2+, since compression of Cs2CoCl4 yields structural transformations associated with change of coordination around Co2+, which are eventually responsible for the intense piezochromism at 7 GPa. This study provides a complete characterization of the electronic and vibrational structures of Cs2CoCl4 in the Pnma phase as a function of the cell volume and the local CoCl4 bond length, RCo-Cl, as well as its corresponding equation of state. In addition, our interest is to elucidate whether the phase transition undergone by Cs2CoCl4 at 7 GPa leads to a perovskite-layer-type structure where Co2+ is sixfold coordinated, decomposes into CsCl+CsCoCl3, or it involves an unknown phase with different coordination sites for Co2+. We show that Co2+ is sixfold coordinated in the high-pressure phase. The analysis of optical spectra and x-ray diffraction data suggests the formation of an interconnected structure of exchange-coupled Co2+ through edge-sharing octahedra at high pressure.

Original languageEnglish
Article number014110
JournalPhysical Review B
Volume95
Issue number1
DOIs
Publication statusPublished - Jan 24 2017
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics

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    Nataf, L., Aguado, F., Hernández, I., Valiente, R., González, J., Sanz-Ortiz, M. N., Wilhelm, H., Jephcoat, A. P., Baudelet, F., & Rodríguez, F. (2017). Volume and pressure dependences of the electronic, vibrational, and crystal structures of C s2CoC l4: Identification of a pressure-induced piezochromic phase at high pressure. Physical Review B, 95(1), [014110]. https://doi.org/10.1103/PhysRevB.95.014110