Synthesis, crystal structure and optical properties of an indium phosphate K3In3P4O16

An alkali-metal indium phosphate crystal, K₃In₃P₄O₁₆, has been synthesized by a high-temperature solution reaction and exhibits a new structure in the family of the alkali-metal indium phosphates system. Single-crystal X-ray diffraction analysis shows the structure to be monoclinic with space group P2₁/n, and the following cell parameters: a=9.7003(18), b=9.8065(18), c=15.855(3) Å, β=90.346(3)°, V=1508.2(5) Å³, Z=4, R=0.0254. It possesses three-dimensional anionic frameworks with tunnels occupied by K⁺ cations running along the a-axis. The emission and absorption spectra of the compound have been investigated. Additionally, the calculations of energy band structure, density of states, dielectric constants and refractive indexes have been performed with the density functional theory method. Also, the two-photon absorption spectrum is simulated by two-band model. The obtained results tend to support the experimental data.