Closer-to-experiment DFT simulation of linear and nonlinear optical properties of MeB4O7 crystals (Me = Sr, Pb, Sn)
https://doi.org/10.1016/j.commatsci.2025.114306
The improved criterion of agreement between ab initio simulation and experiment is tested forthe case of bandgaps in strontium and lead tetraborate. Instead of extracting the bandgap from the band structure diagram, we have compared calculated transmission/absorption spectra with experimental ones, obtaining excellent agreement in case of PBO and fair agreement in case of SBO. Certain disagreement in case of SBO can be ascribed to the contribution of indirect interband transitions. More probably, this disagreement indicates the presence of impurities and stresses the necessity of further improvement of crystal growth technology. The nonlinear optical coefficients of SBO are shown to originate from boron‑oxygen network while those of PBO and and β-SnB4O7 originate from metal ions with their lone pair electrons.