  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 $V_{Si}+Si_{TC}$ 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.
