Speaker
Description
Theoretical modeling of electronic structures of heterostructure composites is a powerful tool for developing novel optical materials. This work presents the results of calculations of the excited electronic states and optical spectra of MoO₄ groups and Bi ions, considered potential luminescence centers in the glass-ceramic composite "KBi(MoO₄)₂ crystal@phosphate-molybdate glass of K₂O-P₂O₅-MoO₃-Bi₂O₃ system."
Atomic and electronic structures of the crystal, glass, and interphase layers were obtained using molecular dynamics and band-periodic density functional theory (DFT) methods. Geometry optimization was performed with the Gaussian software package. Excited electronic states were calculated using time-dependent DFT within a molecular cluster approach and the two-level ONIOM-2 method. The quantum mechanical (QM) region included the MoO₄ groups or Bi ions, while the mechanical (MM) region comprised all other atoms. Electronic embedding accounted for electrostatic interactions between QM and MM regions, treating QM atoms with TD-DFT and MM atoms as partial charges in the quantum-mechanical Hamiltonian.
Calculations were performed on ten structures of the glass and interphase regions, and results were averaged for statistical significance. Similar calculations were done for the MoO₄ groups and Bi ions in the KBi(MoO₄)₂ crystal. The results indicate significant differences in the optical absorption spectra of Bi atoms and MoO₄ groups across different regions of the composite.
Comparisons of the optical spectra for the crystal, glass, and interphase components with experimental data highlight the unique properties of each component. The origin of intrinsic luminescence in phosphate-molybdate glass-ceramics is discussed.
| Type of presence | Presence at Taras Shevchenko National University |
|---|
