The compression mechanism of CrF3

Abstract

The structure of CrF₃ has been studied in the pressure range from ambient to 9.12 GPa by time-of-flight neutron powder diffraction. Rietveld refinements of the crystal structure were performed in the space group R\overline 3 c for all the recorded data sets. It was found that volume reduction is achieved through rotation of the CrF₆ octahedra and that the Cr—F—Cr bond angle decreases from 144.80 (7) to 133.9 (4)° within the investigated pressure range. Furthermore, a small octahedral strain was found to develop during compression. The octahedral strain reflects an elongation of the CrF₆ octahedra along the c-axis direction. The zero-pressure bulk modulus B _o and its pressure derivative B_o^{\prime} were determined to be B _o = 29.2 (4) GPa and B^{\prime}_o = 10.1 (3).