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Volume and pressure dependences of the electronic, vibrational, and crystal structures of C s 2 CoC l 4 : Identification of a pressure-induced piezochromic phase at high pressure

DOI: 10.1103/PhysRevB.95.014110 DOI Help

Authors: Lucie Nataf (Synchrotron Soleil; University of Cantabria) , F. Aguado (University of Cantabria) , Ignacio Hernandez (Universidad de Cantabria; Queen Mary University of London) , R. Valiente (Universidad de Cantabria-IDIVAL) , J. González (University of Cantabria) , M. N. Sanz-ortiz (University of Cantabria; CIC biomaGUNE) , H. Wilhelm (Diamond Light Source) , A. P. Jephcoat (Diamond Light Source) , F. Baudelet (Synchrotron SOLEIL) , Fernando Rodriguez (University of Cantabria)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 95 , PAGES 11

State: Published (Approved)
Published: January 2017
Diamond Proposal Number(s): 832 , 891 , 1655 , 6078 , 9985 , 16089 , 20786

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 Cs2 CoCl4 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.

Subject Areas: Materials, Physics, Chemistry

Diamond Offline Facilities: Spectrometer for ruby luminescence
Instruments: I15-Extreme Conditions

Other Facilities: SOLEIL