Conservation of dielectric constant upon amorphization in perovskite   oxides
  We report calculations indicating that amorphous RAO$_3$ oxides, with R and A trivalent cations, have approximately the same static dielectric constant as their perovskite crystal phase. The effect is due to the disorder-activated polar response of non-polar crystal modes at low frequency, which compensates a moderate but appreciable reduction of the ionic dynamical charges. The dielectric response was studied via density-functional perturbation theory. Amorphous samples were generated by molecular dynamics melt-and-quench simulations. 
Pietro Delugas, Vincenzo Fiorentini, Alessio Filippetti, Geoffrey   Pourtois