Energetics of Cs in Sigma3 grain boundary of 3C-SiC

Energetics of Cs defects at Sigma3 grain boundaries of 3C-SiC has been studied using density functional theory to understand the role of the grain boundaries in Cs diffusion and its eventual release from the tristructural isotropic fuel particles (TRISO). Cs is shown to be much more stable at the Sigma3 grain boundary than in bulk of SiC with a significant decrease (7-17eV) in the formation energies at the grain boundaries than in bulk. It is found to have even lower formation energies than those of Ag at the Sigma3 grain boundaries, while this trend was opposite in the bulk SiC as demonstrate previously from similar density functional theory calculations. Based on these results, a possible route to control Cs release from SiC layer via grain-boundary-engineering is suggested.