The pre-exponential factor in the conductivity of liquid semiconductors

Abstract

Consideration is given to certain liquids undergoing a metal-insulator transition with change of volume or composition. In the semiconducting phase a conductivity of the form σ =σ₀ exp(- E/kT) is observed, and it is assumed that electrons move at a mobility edge. The value of the pre-exponential factor a. is discussed in terms of whether it should approximate to the Mott minimum conductivity value, σ_min, or to a smaller one. The nature of the Anderson transition for very small values of the inelastic diffusion length L _i is described and the value of L _i for amorphous and liquid metals is discussed. Also considered is the 'dielectric catastrophe', observed in solutions of potassium in liquid KCl and of sodium in ammonia. in terms of the Clausius-Mossotti formula.