Angular Jahn-Teller Effect and Photoluminescence of the Tetrahedral Coordinated Mn Activators in Solids-A First-Principles Study.

First-principles calculations based on density functional theory have been performed to investigate the electronic structure, excited-state Jahn-Teller distortion, and photoluminescence of the multielectron system of the strongly covalent tetrahedral coordinated Mn activator in solids. The electronic structure of the T and A/E excited states is analyzed, and Slater's transition-state method and occupation matrix control methodology are applied to deal with the spin contamination in the lower-spin excited states, which is due to the mixing of the ground state of the same spin projection number. In a series of covalent tetrahedral coordinations, the A → T and A/E excitations and the T → A emission energies are obtained and compared to the reported experimental results. The nephelauxetic effect follows O < S ≈ Se < N, and the larger nephelauxetic effect and crystal field strength lead to the red-shifted emission of nitride phosphors. The Jahn-Teller distortion of the T states is dominated by the -type angular distortion of the [Mn] moiety ( being the ligand), which accounts for the small Stokes shift of tetrahedral coordinated Mn. The results show that the ground- and excited-state electronic and geometric structures and the luminescent property of tetrahedral coordinated Mn can be reliably predicted. The method can be further explored to interpret and discriminate the luminescent properties of materials containing a variety of different Mn sites and complexes and even other transition metals.