Nonsimultaneous Place Exchange: A Microscopic High Field Transport Mechanism in Solids

Abstract

A nonsimultaneous place‐exchange mechanism is postulated whereby ionic motion takes place by means of elemental excitations labeled “hopons.” A hopon is defined to be the thermally activated electric field‐modified motion of a localized place exchange between oppositely charged ionic constituents in a compound. The virtual defect associated with hopon motion is considered to be a highly localized disturbance which jumps statistically with time from place to place in the medium, although in certain cases it may be a somewhat more extended wavelike disturbance which propagates with a finite velocity through the medium. These two possibilities are referred to respectively as “noncollective” and “collective” hopon transport mechanisms. Some of the ramifications of hopons for the formation of anodic oxides on metals are examined, including consideration of where the new oxide layers are formed, the relative transport numbers for anions and cations through the oxide, the preservation of microscopic order in the anion and the cation sublattices in the oxide, and the energies and the kinetics for anodic oxide growth.