Eu³⁺-doped bismuth silicate crystal structure and Mulliken charge analysis

The effects of Eu³⁺ doping on the crystal structure and charge distribution of Bi₄Si₃O₁₂ (BSO) bisilicate, based on first principles and density functional theory (DFT), were calculated and analyzed using Materials Studio software. The effect of different proportions (1/12, 1/6 and 1/3) of Eu³⁺ doping on BSO crystals was investigated using the virtual crystal approximation method. Through Mulliken charge analysis, it is found that a high proportion of Eu³⁺ doping will destroy the symmetry of the crystal structure. With an increase of the Eu³⁺-doping ratio, the Eu-O bond length first increased and then decreased, showing the characteristics of covalent bonds, and the Eu-O bond length reached the minimum value when the Eu³⁺-doping ratio was increased to 1/3. With an increase in the Eu³⁺-doping ratio, the Bi-O bond length decreases sequentially and also reaches the minimum value when the Eu³⁺-doping ratio was increased to 1/3. This indicates that the covalence between the Eu-O and Bi-O atoms is enhanced when the doping ratio is 1/3 when BSO crystals are doped with Eu³⁺.