Effect of Pressure on the Diffusion of Gold in Lead to 50 kbar

We have measured the diffusion of gold in lead to pressures of 46 kbar and temperatures of 420 °C using a radioactive-tracer technique. The data were analyzed assuming a single effective mechanism of diffusion with a temperature- and pressure-dependent activation volume. The earlier data on the diffusion of silver in lead by Curtin, Decker, and Vanfleet were also analyzed in a similar manner. The activation energy and activation volume at the melting point and atmospheric pressure are, respectively, $\Delta H=9.48\mathrm{}\pm 0.30$ kcal per mole, $\frac{\Delta V}{V_0}=0.28\mathrm{}\pm 0.03$ for Au in Pb: $\Delta H=14.63\mathrm{}\pm 0.24$ kcal per mole, $\frac{\Delta V}{V_0}=0.34\mathrm{}\pm 0.04$ for Ag in Pb. Although no definite conclusion as to the specific nature of the diffusion mechanism can be drawn, the results are not inconsistent with an interstitial-substitutional double mechanism.