Spectroscopy of YAl₃(BO₃)₄:Cr³⁺ crystals following first principles and crystal field calculations

The CASTEP module of the Materials Studio package was used for calculations of the structural, electronic and optical properties of pure and Cr ³⁺-doped YAl₃(BO₃)₄ (YAB). The exchange-correlation effects were treated within the generalized gradient approximation with the Perdew-Burke-Ernzerhof functional. The Monkhorst-Pack scheme k-points grid sampling was set at 3 × 3 × 4 for the Brillouin zone. The plane-wave basis set energy cutoff was set at 340 eV; ultrasoft pseudopotentials were used for all chemical elements. The convergence parameters were as follows: total energy tolerance 1 × 10^-5 eV/atom, maximum force tolerance 0.03 eV/nm, maximal stress component 0.05 GPa and maximal displacement 0.001 . The principal absorption peaks of the studied crystal were identified. The influence of 532 nm cw, 300 mW laser radiation on the observed absorptions was studied.