Effect of Hydrostatic Pressure on the Self-Diffusion Rate in Single Crystals of Gold

The rate of self-diffusion in gold was measured by the radioactive-tracer-lathe-sectioning technique at 860, 910, and 960°C and at hydrostatic pressures from 2.00 to 9.08 kbar. The diffusion rate was observed to decrease with increased pressure, and the activation volume for self-diffusion was determined to be 7.2±0.4 ${\mathrm{cm}}^3$/mole. This value is in good agreement with the sum of the experimental values of the activation volumes of formation and motion in gold, the experimental values of the activation volumes in other fcc metals, and many of the theoretical values calculated for copper. The present value also is in fair-to-excellent agreement with the various expressions relating the activation volume to other experimentally derived quantities. The limiting source of error in pressure-diffusion experiments of the present type was found to be in controlling the measurement, reproducibility, and uniformity of the temperature.