A Theoretical Study on the Structural and Energy Spectral Properties of Ce³⁺ Ions Doped in Various Fluoride Compounds

Geometry optimization and wave function-based complete-active-space self-consistent field-embedded cluster calculations have been performed for a series of Ce³⁺-doped fluoride compounds (CaF₂, YF₃, LaF₃, KMgF₃, LiYF₄, K₂YF₅, and KY₃F₁₀) to investigate local coordination structures, crystal field parameters, and 5d¹ energy-level structures of doping Ce³⁺ ions. The crystal-field parameters of Ce³⁺ are extracted from the calculated energies and wave functions. The calculated crystal-field parameters and 5d¹ energy-level structures show excellent consistency with the experimental results. Our calculations show that the onset of 4f → 5d absorption, which is important in phosphors and scintillators, can be well-predicted. Apart from that, the distortion of local structure due to doping, the wave functions, and the crystal-field parameters of 4f¹ and 5d¹ states of Ce³⁺ in the hosts can be obtained. Those can seldom be obtained by fitting empirical crystal-field Hamiltonian to experimental data but are required by some detailed theoretical analysis, such as the calculation of transition intensities and hyperfine splittings. The obtained crystal-field parameters of Ce³⁺ may also be useful for other lanthanide ions in the same hosts.