La2SrB8O16: A new rare earth borate with [B8O20]16− groups exhibiting a deep ultraviolet cutoff edge

Abstract A new rare-earth borate crystal La2SrB8O16 (LSB8) has been grown by means of spontaneous crystallization for the first time. It crystallizes in triclinic space group P 1 ¯ (No. 2), and the lattice parameters are a ​= ​4.7512(4) A, b ​= ​7.1202(5) A, c ​= ​8.0147(5) A, α ​= ​76.629(2)°, β ​= ​77.934(2)°, γ ​= ​86.588(3)°, and Z ​= ​1, respectively. LSB8 has a layered structure, which is constituted of centrosymmetric B8O20 groups. Its spectral characteristics were detailedly investigated. The electronic band, refractive indices, and density state of LSB8 were calculated according to the first principles.