Pressure Dependence of the Structure of Hybrid Improper Ferroelectric A₃B₂O₇

    Pressure and temperature-dependent structural measurements are used to explore the complex phase diagram of the A₃B₂O₇ improper ferroelectric system. Single crystal x-ray and powder neutron diffraction measurements are combined with x-ray powder diffraction survey measurements to extract the space groups under varying conditions. Neutron measurements sensitive to all atomic motions, including oxygen, are used to track polyhedral rotations. In parallel, DFT simulations are being used to determine possible competing phases.   This synergistic loop is providing information on the pressure-induced phase transitions.