Interstitial Diffusion of Gold and Silver in Indium

The diffusivities $D$ of silver in the $c$ and $a$ directions of indium and gold in randomly oriented single crystals of indium have been measured by a radioactive-tracer technique. They are described by: ${D_{\frac{\mathrm{Ag}}{\mathrm{In}}}}^{\mathrm{a}}=5.2\mathrm{}\times {10}^{-1\mathrm{}} \exp (-\frac{12800}{\mathrm{RT}})$, ${D_{\frac{\mathrm{Ag}}{\mathrm{In}}}}^{\mathrm{c}}=1.1\mathrm{}\times {10}^{-1\mathrm{}} \exp (-\frac{11500}{\mathrm{RT}})$, and $D_{\frac{\mathrm{Au}}{\mathrm{In}}}=9\mathrm{}\times {10}^{-3\mathrm{}} \exp (-\frac{6700}{\mathrm{RT}})$. The rates of diffusion of silver and gold in indium are thus several orders of magnitude greater than the self-diffusion rate of indium. These results indicate that gold and silver are dissolved at least partly in the interstitial state, in agreement with a theory which predicts that $d-d$ correlation forces should cause dissolved noble metals to favor interstitial sites in indium.