A study of the effects of high pressure gradients revealed that the iodide dissociated, with metal ions collecting irreversibly in the low-pressure area and halide ions collecting in the high-pressure area; where they combined to form molecular halogen. The Ag was then reduced in incident light. Because of the low activation energy for migration (0.2eV for a pressure gradient of 30kbar), it was suggested that transport occurred in regions of misorientation; such as grain boundaries and dislocation zones. High Pressure Study of AgI: Diffusion in a Pressure Gradient. R.N.Schock, S.Katz: Journal of Physics and Chemistry of Solids, 1967, 28, 1985-93