Chemical Design Rule for Ultraviolet-Emitting Color Centers: The Role of Host Ionicity

Here we show that the energy of zero-phonon lines (ZPLs) is not controlled by the bandgap alone, but is governed by the host bonding character (covalent versus ionic) through the bonding–antibonding splitting of lattice divacancy-derived defect states.

In covalent diamond, the divacancy yields only a 0.79 eV separation within the optical two-level manifold, so that most established centers exhibit ZPLs predominantly in the near-infrared or visible. By contrast, in ionic cubic boron nitride (c-BN), the corresponding divacancy splitting can reach 5.61 eV, naturally pushing the analogous transitions into the UV band. Building on this basic understanding, we establish a unified rule, combining impurity-associated atomic potential, lattice strain, and orbital hybridization, to predict ZPL trends of vacancy-impurity-vacancy (XV) centers in c-BN.