The High-Pressure Phase Transition in Jamesonite: A Single-Crystal Synchrotron X-ray Diffraction Study

The high-pressure behavior of jamesonite (FePb4Sb6S14, a = 4.08(3) angstrom, b = 19.08(3) angstrom, c = 15.67(3) angstrom, beta= 91.89 degrees, space group P2(1)/c) has been investigated using in situ HP synchrotron X-ray single-crystal diffraction up to similar to 17 GPa with a diamond anvil cell under hydrostatic conditions. Results of the volume isothermal equation of state (EoS), determined by fitting the P-V data with a third-order Birch-Murnaghan (BM) EoS, are V-0 = 1207.1(4) angstrom(3), K-0 = 36(1) GPa and K' = 5.7(7). At high pressure, jamesonite undergoes a phase transition to an orthorhombic structure with a Pmcb space group (beta-jamesonite). The analysis of beta-jamesonite's compressibility up to 16.6 GPa, studied by fitting the data with a second-order BM-EoS, gives V-0 = 1027(2) angstrom(3), K-0 = 74(2) GPa. The comparison of the structural refinements at different pressures indicates that Fe, Pb and Sb do not change their coordination number over the whole investigated P range, respectively, 6 for Fe, 7 and 8 for Pb and 5 + 2 for Sb. However, a significant change occurs on the orientation of Sb lone electron pairs upon the phase transition in accordance with the change in symmetry. Furthermore, a discontinuity in the Fe chain evolution at the transition pressure is observed.