Energetics and structure of ⟨0 0 1⟩ tilt grain boundaries in SiC

We have developed a scheme, based on molecular dynamics, that allows finding minimum energy structures of grain boundaries (GBs) with relatively large cell of non-identical displacements. This scheme has been used to study symmetric < 0 0 1 > tilt GBs in cubic SiC. We analyze atomic configurations of dislocation cores found in low-angle GBs and we report structural units found in high-angle GBs. In contrast to what had been previously assumed we find that the lowest energy structures often do not favor perfect coordination of GB atoms and that most of the analyzed GBs contain 6- and 7-atom rings. We tested the applicability of existing empirical potentials to studies of high-symmetry GB structures in SiC and we found the Tersoff potential to be most appropriate. Knowledge of detailed atomic structures of GBs is essential for future studies of GB-controlled phenomena in SiC, such as diffusion of metallic fission product through this material or GB strengthening.