Quantum chemistry and QSPR study on relationship between crystal structure and emission wavelength of Eu²⁺-doped phosphors

The relationship between crystal structures and emission properties has been computationally investigated for Eu ²⁺-doped phosphors. The electronic structure of the Eu ²⁺-doped BaMgAl ₁₀O ₁₇ phosphor was analyzed by using the quantum chemistry method. The different effects of O and Ba atoms on the Eu 5d states were determined. The presence of O and Ba atoms increases and decreases the energy level of the Eu 5d orbital by forming anti-bonding and bonding interactions, respectively. According to the electronic-structure analysis, the structure index that represents the local geometrical information of the Eu atom was defined. The relationship between the crystal structures and the emission wavelengths of the 16 Eu ²⁺-doped oxide phosphors were studied by using the quantitative structure-property relationship (QSPR). The QSPR model suggested that the both O and alkaline-earth atoms around the Eu atom are of importance in the determination of the emission wavelength. The interaction between the Eu and the nearest O atoms make the Eu ²⁺ emission wavelength short. On the other hand, the interaction from the alkaline-earth atoms around the Eu atom lengthens the Eu ²⁺ emission wavelength. This evaluation method is useful in selecting the host material that indicates a desirable emission wavelength of the Eu ²⁺-doped phosphors.