  Study and design of magneto-optically active single point defects in
semiconductors are rapidly growing fields due to their potential in quantum bit
and single photon emitter applications. Detailed understanding of the
properties of candidate defects is essential for these applications, and
requires the identification of the defects microscopic configuration and
electronic structure. Multi-component semiconductors often host two or more
non-equivalent configurations of point defects. These configurations generally
exhibit similar electronic structure and basic functionalities, however, they
differ in details that are of great importance whenever single defect
applications are considered. Identification of non-equivalent configurations of
point defects is thus essential for successful single defect manipulation and
application. A promising way to identify defects is via comparison of
experimental measurements and results of first-principle calculations. We
investigate a possibility to produce accurate ab initio data for zero-phonon
lines and hyperfine coupling parameters that are required for systematic
quantum bit search. We focus on properties relevant for the possible use of the
divacancy defect in quantum bits in 4H-SiC. We provide a decisive
identification of divacancy configurations in 4H-SiC and clarify differences in
prior predictions of 4H-SiC divacancy zero-phonon photoluminescence lines.
