Disordered pyrochlore CsMgInF6 at high pressures

High pressure behaviour of disordered pyrochlore CsMgInF6 (Pnma, Z=4) has been studied with powder and single-crystal X-ray diffraction to 8.0 and 6.94 GPa, respectively, in diamond anvil cells at room temperature. The material is structurally stable to at least 8.0 GPa with no ordering of the In3+ and Mg2+ cations. The P–V data are fitted by a Birch–Murnaghan equation of state with the zero-pressure bulk modulus B0=33.4(3) GPa and the unit-cell volume at ambient pressure V0=603.2(4) Å3 for the first pressure derivative of the bulk modulus B′=4.00. The major contribution to the bulk compressibility arises from the changes in the coordination sphere around the Cs atoms. The effect of hydrostatic pressure on the crystal structure of CsMgInF6 is comparable to the effect of chemical pressure induced by the incorporation of ions of different sizes into the A and B sites in defect AB2+B′3+F6 pyrochlores.

Crystal structure of CsMgInF6 (Pnma, Z=4) at 6.04 GPa. Yellow, red, and blue symbols represent the Cs, (Mg/In), and F atoms, respectively. Octahedra around the (In1/Mg1) and (In2/Mg2) atoms are drawn gray and cyan, respectively.Figure optionsDownload as PowerPoint slide