First-principles investigation of site preference and diffusion behaviors of carbon in copper

Abstract

Using a first-principles method, we have investigated site preference and diffusion properties of carbon (C) in copper (Cu). A single C atom energetically prefers to occupy the octahedral interstitial site (OIS) instead of the tetrahedral interstitial site. Double C atoms tend to be paired up at the nearest neighboring OIS’s along the 〈100〉 direction mediated by a bridging Cu atom with a distance of 3.85Å and a binding energy of 0.15eV. This suggests that an indirectly attractive interaction between C atoms exists, which might lead to a local higher concentration of C in Cu. We demonstrate that the OIS→OIS path is the optimal diffusion path of C in Cu with diffusion barrier of 0.93eV. By the estimation of pre-exponential factor according to a classical thermodynamics model, the diffusion coefficient as a function of temperature has been determined, which is 3.68×10−15m2/s at a typical temperature of 600K. The results provide a good reference to understand the behavior of C in Cu.