Diffusion of Ag in Pb in the kilobar range

An accurate tracer-diffusion experiment was carried out on the system Pb(Ag) at pressures $P$ between atmospheric pressure and 8.6 kbar. Activation-energy $\Delta H$ values between about 13.4 and 16.7 kcal/mole and an activation volume $\Delta V=0.37\mathrm{}$ atomic volumes were obtained. Although the general trend of the activation energy as a function of $P$ extrapolates well the results published by Curtin et al. between 11.9 and 39.2 kbar, the $\Delta H-\mathrm{vs}-P$ plot does not seem to be linear, and thus reinforces previous doubts on the singleness of the diffusion mechanism.