  Spin defects in wide-bandgap semiconductors provide a promising platform to
create qubits for quantum technologies. Their synthesis, however, presents
considerable challenges, and the mechanisms responsible for their generation or
annihilation are poorly understood. Here, we elucidate spin defect formation
processes in a binary crystal for a key qubit candidate--the divacancy complex
(VV) in silicon carbide (SiC). Using atomistic models, enhanced sampling
simulations, and density functional theory calculations, we find that VV
formation is a thermally activated process that competes with the conversion of
silicon ($V_{Si}$) to carbon monovacancies ($V_{C}$), and that VV reorientation
can occur without dissociation. We also find that increasing the concentration
of $V_{Si}$ relative to $V_{C}$ favors the formation of divacancies. Moreover,
we identify pathways to create spin defects consisting of antisite-double
vacancy complexes and determine their electronic properties. The detailed view
of the mechanisms that underpin the formation and dynamics of spin defects
presented here may facilitate the realization of qubits in an industrially
relevant material.
