A scheme, based upon molecular dynamics, was developed that permitted the finding of minimum-energy structures of grain boundaries using relatively large non-identical displacements. This scheme was used to study symmetrical <001> tilt grain boundaries in cubic SiC. The atomic configurations of dislocation cores found in low-angle grain boundaries were analyzed and the structural units found in high-angle grain boundaries were reported. In contrast to what had been previously assumed, it was found that the lowest energy structures often did not favour a perfect coordination of grain-boundary atoms and that most of the grain boundaries analyzed contained 6- and 7-atom rings. The applicability of existing empirical potentials to studies of high-symmetry grain boundary structures in SiC was tested and the Tersoff potential was found to be most appropriate. Knowledge of detailed atomic structures of grain boundaries was essential for future studies of grain boundary-controlled phenomena in SiC, such as diffusion of metallic fission products through this material or grain boundary strengthening.

Energetics and Structure of <001> Tilt Grain Boundaries in SiC. M.Wojdyr, S.Khalil, Y.Liu, I.Szlufarska: Modelling and Simulation in Materials Science and Engineering, 2010, 18[7], 075009