A point dipole model for the spread of activation energies in glassy dielectrics

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Abstract
An electrostatic interaction model is presented to account for a distribution of activation energies in a conducting dielectric. Positive and negative charge pairs surrounding a given site are treated as point dipoles, and the resulting strong local field raises or lowers the barrier to charge migration at that site. The calculations result in normal distributions of activation energies and the breadth of the distributions increases steeply with charge carrier concentration, as observed for ion migration in glasses. The upper half of the distribution is assumed to be ineffective, and a half-normal distribution of Debye terms in the modulus sum is shown to give approximate agreement with dielectric loss measurements on a soda silica glass.