Effect of Pressure on the Low Frequency Dielectric Constant of Ionic Crystals

Data on the pressure dependence of the dielectric constant of MgO, LiF, NaCl, KCl and KBr at 1000 c. p. s. and room temperature are given as a function of hydrostatic pressure from 0 to 8000 bars. The dielectric constants are found to decrease with an initial slope ({) }ₓ ranging from -0. 3210^-5 bar^-1 in the case of MgO to -1. 1710^-5 bar^-1 in the case of KBr. Present lattice theories are only capable of explaining these data if the inner field decreases with increasing pressure.