The Electronic Structural and Defect-Induced Absorption Properties of a Ca$_{2}$B$_{10}$O$_{14}$F$_{6}$ Crystal

Comprehensive ab initio electronic structure calculations were performed for a newly developed deep-ultraviolet (DUV) non-linear optical (NLO) crystal Ca$_{2}$B$_{10}$O$_{14}$F$_{6}$ (CBOF) using the first principle method. Fifteen point defects including interstitial, vacancy, antisite, Frenkel, and Schottky of Ca, O, F, and B atoms in CBOF were thoroughly investigated as well as their effects on the optical absorption properties. Their formation energies and the equilibrium concentrations were also calculated by ab initio total energy calculations. The growth morphology was quantitatively analyzed using the Hartman–Perdok approach. The formation energy of interstitial F (Fi) and antisite defect O$_{F}$ were calculated to be approximately 0.33 eV and 0.83 eV, suggesting that they might be the dominant defects in the CBOF material. The absorption centers might be induced by the O and F vacancies (V$_{F}$, V$_{O}$), interstitial B and O (O$_{i}$, B$_{i}$), and the antisite defect O substitute of F (O$_{F}$), which might be responsible for lowering the damage threshold of CBOF. The ionic conductivity might be increased by the Ca vacancy (V$_{ca}$), and, therefore, the laser-induced damage threshold decreases.