Abstract
Glasses containing transition metal ions show the Jonscher 'universal dynamic response' i.e. the ac conductivity, as a function of frequency, is given by (sigma) ((omega) ) equals (sigma) (0) + (omega) s, where (sigma) (0) is the dc conductivity, and the exponent s (<EQ1) generally decreases with increasing temperature. It is found that s(T) exhibits a minimum in V2O5 - P2O5 glasses. This behavior can be described in terms of overlapping polaron tunnelling model.In the model the polaron hopping energy is reduced when polaron wells in the pair of vanadium ions do overlap. The power law of ac conductivity is observed in the high frequency range when the hopping occurs only between the nearest sites. Distances between vanadium atoms and their distributions have been evaluated from molecular dynamic (MD) simulations. The MD simulations, according to the Andersen algorithm, have been performed in the isobaric-isoenthalpic ensemble. The atoms were assumed to interact by a two-body potential, with Abrahamson parameterization. In the base of the simulation results the polaron parameters have been determined.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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