  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.
