First-principles calculations of photoluminescence and defect states of Ce3+ -doped (Ca/Sr)2B5O9Cl

Reliable predictions of electronic levels, excited-state geometric relaxation, and the relative energies of ground and excited levels to host band edges are of paramount importance for $\mathrm{C}{\mathrm{e}}^{3+}$-doped luminescent materials. By combining the constrained occupancy approach and the hybrid density functional calculation in the framework of a generalized Kohn-Sham formalism, we derived a calculation scheme for the band gap of the host material, the equilibrium configurations of ground-state $\mathrm{C}{\mathrm{e}}^{3+}$ and excited-state ($\mathrm{C}{\mathrm{e}}^{3+}$)*, and their relative energies with respect to host band edges in terms of hole capture or electron ionization for $\mathrm{C}{\mathrm{e}}^{3+}$ in ${M}_{2}{\mathrm{B}}_{5}{\mathrm{O}}_{9}\mathrm{Cl}$ ($M=\mathrm{Ca}$, Sr) charge compensated by $\mathrm{N}{\mathrm{a}}^{+}$. The results of first-principles calculations for $4f\ensuremath{\rightarrow}5d$ excitations, Stokes shifts, and the relative position of $5d$ levels to conduction-band edge agree well with experiments. The moderate computational cost of the present scheme, which can be applied in efficient prediction of the optical properties of many different Ce-doped materials, is of important value in screening potential lanthanide-doped scintillators and phosphors from minimal information about the host crystal structure.