The canonical HF molecular orbitals initially delocalized over the whole system, are localized to define a local fragment and its environment, using the maximally localized Wannier functions (MLWFs) obtained from the mean-field orbitals using wannier90 56 code via the pyWannier90 interface. After the orbital localization, choosing a physically motivated impurity cluster is a key step in DMET calculations. The impurity cluster is defined by a set of atoms on which the MLWFs are spatially localized. Since we are interested in the defect-localized transitions, a reasonable choice of the impurity cluster would be the one that includes the atoms comprising and surrounding the defect center. We consider a 16 atom impurity cluster (N C 15 ) that includes the N atom and the C atoms closest to the N and the vacancy site. In Fig. , all 3 supercells considered are shown along with the atoms within the impurity cluster specifically highlighted. then projected onto the combined space of fragment and bath orbitals and the high-level wave function is determined using CASSCF, followed by NEVPT2 for the energy calculation. The CAS-DMET (using CASSCF as the impurity solver) and NEVPT2-DMET (using NEVPT2