| Abstrakt: |
Lanthanide luminescent materials play key roles in modern society, but their first‐principles treatment remains a great challenge due to complex manifold of electronic excited states and the difficulty in performing excited state structural relaxations that is necessary to model luminescent properties. Herein, we propose a practical approach that combines embedded cluster model (ECM) based multi‐configurational wave function theory (WFT) and occupancy constrained density‐functional theory plus the Hubbard Ucorrection (OC‐DFT + U) to treat lanthanide doped luminescent materials, using LaF3:Ce3+, a typical scintillator with low symmetry, as a case study. We show that the combined approach yields accurate absorption energies with an error on the order of 200 cm−1, but the emission energies are significantly underestimated, the origin of which is further clarified by vibrationally resolved absorption and emission spectra calculation. This work demonstrates the possibility of combining ECM‐based wave function theory and periodic DFT into a comprehensive computational scheme for lanthanide luminescent materials and highlights the limitations of the current implementation of OC‐DFT + Ufor excited state structural optimization. We combine cluster‐based quantum chemistry method with periodic DFT calculation into a practical approach for excited states of lanthanide luminescent materials and illustrate the idea using LaF3:Ce3+. Absorption energies are quite accurate but emission energies are underestimated. Optical spectra calculation then reveals that this is due to excited state over‐relaxation predicted by occupancy constrained DFT plus the Hubbard Ucorrection |
Plný text