New bismuth borophosphate Bi₄BPO₁₀: Synthesis, crystal structure, optical and band structure analysis

New bismuth borophosphate Bi₄BPO₁₀ was obtained by spontaneous crystallization from the melt of correspondent composition at 804 °C. Crystal structure with orthorhombic lattice parameters: a = 22.5731(3) Å, b = 14.0523(2) Å, c = 5.5149(1) Å, V = 1749.34(4), Z = 8, SG Pcab was determined by X-ray powder diffraction technique. The [Bi₂O₂]²⁺ -layers, which are typical for bismuth oxide compounds, transform into cationic endless strips of 4 bismuth atoms width directed along the c-axis in Bi₄BPO₁₀. The strips combining stacks are separated by flat triangle [BO₃]³⁻ -anions within stacks. Neighboring stacks are separated by tetrahedral [PO₄]³⁻-anions and shifted relatively to each other. Bismuth atoms are placed in 5–7 vertex oxygen irregular polyhedra. Bi₄BPO₁₀ is stable up to 812 °C, then melts according to the peritectic law. The absorption spectrum in the range 350–700 nm was obtained and the width of the forbidden band was estimated as 3.46 eV. The band electronic structure of Bi₄BPO₁₀ was modeled using DFT approach. The calculated band gap (3.56 eV) is in good agreement with the experimentally obtained data. - Graphical abstract: Display Omitted - Highlights: • New bismuth borophosphate with composition Bi₄BPO₁₀ was synthesized. • The crystal structure was determined by X-ray powder diffraction technique. • Bismuth-oxygen part [Bi₄O₃]⁶⁺ forms endless strips of 4 bismuth atoms width. • Electronic structure was modeled by DFT method. • The calculated band gap (3.56 eV) is very close to the experimental one (3.46 eV)