Earlier measurements of thermally stimulated depolarization currents in cubic PbF2 containing small rare earth ions have led to the determination of the pre-exponential factor tau(0) and the activation energy E involved in the Arrhenius relation tau=tau(0)exp(E/kT). Here, we show that these parameters are interconnected in a way governed by bulk properties. This corroborates with a very recent finding (Solid State Ionics, 179 (2008) 438) which showed that, for various defect processes, the ratio of the activation volume over the corresponding energy is also equal to a bulk quantity. (C) 2008 Elsevier B.V. All rights reserved.