The compressibility mechanism of Li3Na3In2F12 garnet

The high pressure behaviour of Li3Na3In2F12 garnet () is studied up to 9.2 GPa at room temperature in diamond anvil cells using x-ray diffraction. Its equation of state to 9.2 GPa and the pressure dependences of the structural parameters to 4.07 GPa are determined from synchrotron angle-dispersive powder and laboratory single-crystal data, respectively. No indication of any structural phase transition in this material has been found up to 9.2 GPa. The fitting of the Murnaghan equation of state yields B0 = 36.2(5) GPa, B' = 5.38(18), and V0 = 2051.76(0.69) A3. The compressibility mechanism of Li3Na3In2F12 is attributed to the substantial bending of the In–F–Li angles linking the InF6 octahedra and LiF4 tetrahedra. The most compressible polyhedral units are the NaF8 triangulated dodecahedra. These results are discussed in relation to previous high pressure photoluminescence measurements and compared with the high pressure behaviour of silicate garnets.