Carbon self-diffusion in a natural diamond

We report experimentally determined self-diffusion coefficients for carbon in a type-IaA diamond at pressure and temperature conditions within diamond stability field at $10\mathrm{GPa}$ and $2075–2375\mathrm{K}$. The activation energy of diffusion is $6.8\pm 1.6\mathrm{eV}$ and a preexponent constant is of $4.1\times {10}^{-5}{\mathrm{m}}^2∕\mathrm{s}$ $[\ln (-10.1\pm 2.0){\mathrm{m}}^2∕\mathrm{s}]$. The activation energy is approximately 30% lower than results predicted previously from ab initio calculations.

Figure 1

An IR absorption spectrum of the diamond normalized to $1\mathrm{cm}$ thickness. Nitrogen concentration was determined using the calibration of Boyd et al. (Ref. 5).

Figure 2

A schematic cross-section illustration of the experimental assembly.

Figure 3

A diffusion model fit to a concentration profile. Circles are fraction of ${}^{13}\mathrm{C}$ measured by SIMS. The line is the best-fit model as discussed in the text.

Figure 4

Diffusion coefficients determined at $2073\mathrm{K}$, $10\mathrm{GPa}$ is plotted against experiment duration. No systematic changes are seen.

Figure 5

An Arrhenius plot of carbon self-diffusion coefficient at $10\mathrm{GPa}$. The solid line is the best-fit regression accounting for the uncertainty in temperature and diffusion coefficients.