Theoretical study of the recombination of Frenkel pairs in irradiated silicon carbide

The recombination of Frenkel pairs resulting from low energy recoils in 3C-SiC has been investigated using first principles and Nudged Elastic Band calculations. Several recombination mechanisms have been obtained, involving direct interstitial migration, atoms exchange, or concerted displacements, with activation energies ranging from 0.65 eV to 1.84 eV. These results are in agreement with experimental activation energies. We have determined the lifetime of the VSi + SiTC Frenkel pair, by computing phonons and the Arrhenius prefactor. The vibrational contributions to the free energy barrier have been shown to be negligible in that case.