Force field, external particle migration

The physical separation of charge represented allows externally apphed electric field forces to act on the solution in the diffuse layer. There are two phenomena associated with the electric double layer that are relevant electrophoresis when a particle is moved by an electric field relative to the bulk and electroosmosis, sometimes called electroendosmosis, when bulk fluid migrates with respect to an immobilized charged surface. 

This mechanism operates stochastically in the absence of correlations and external driving forces. If the vacancy, for instance, is effectively positively charged and an external field is applied, then the vacancy migrates to the side of the negative pole (opposite to the direction of A-migration). This mass transport can be described very much more simply from the point of view of the vacancy defect, rather than by considering the actual trajectories of the substantial A-particles involved. 

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