High-pressure behaviour of synthetic weberite-type Mn~(2+)_2Sb~(5+)_2O_7: An in situ single-crystal X-ray study

摘要

An in situ high-pressure X-ray diffraction study has been carried out at room temperature up to 9.26 GPa on synthetic Mn_2Sb_2O_7 having a weberite-3T structure. A 2nd-order Birch—Murnaghan Equation of State (EoS) was used to refine the pressure—volume data. The refinement of the unit-cell volume and of the isothermal bulk modulus at room pressure leads to: V_0 = 782.7(2), K_(T0) = 150( 1) GPa. Unit-cell parameters decrease gradually as a function of pressure with a bulk modulus anisotropy scheme, with a being the softest direction. The overall mean polyhedral distances are quite constant, indicating a scarce compressibility of both the A and B polyhedra in the pressure range investigated. The compressional behaviour of Mn_2Sb_2O_7 is compared with that shown by ingersonite, Ca_3MnSb_4O_(14), and synthetic orthorhombic