First-principles study on electronic structure and optical properties of Mn-doped Ba3V2O8

The electronic structure and optical properties of Mn-doped Ba 3 V 2 O 8 , a promising cobalt-free pigment, are investigated using first-principles calculations to elucidate the microscopic mechanism of its vivid blue coloration.Structural optimization done by the pseudopotential method, combined with high-precision all-electron band calculations (FLAPW method) reveals the interplay between local lattice distortion and optical response.The results demonstrate that the substitution of V 5+ with Mn 5+ (3d 2 ) introduces spin-polarized impurity states within the band gap.These mid-gap states arise intrinsically from the crystal field splitting of the Mn orbitals into occupied e and unoccupied t 2 levels.Crucially, the [MnO 4 ] 3-tetrahedra undergo significant structural distortion, lowering the local symmetry from T d to C 1 .While this distortion is not the primary origin of the impurity levels, it plays a decisive role in governing the optical transition probabilities.The symmetry breaking enhances the hybridization between Mn 3d and O 2p orbitals, relaxing the selection rules for d-d transitions.Consequently, a distinct absorption peak arises at approximately 1.6 eV, which is responsible for the blue color, alongside a charge-transfer transition around 3.3 eV.Furthermore, the distortion induces strong optical anisotropy, manifested as a significant splitting of the dielectric function along the principal optical axes.This study provides a comprehensive theoretical framework linking the local geometric distortion to the intense and anisotropic optical response of Mn-doped Ba 3 V 2 O 8 .