Crystal growth, characterization and theoretical studies of the noncentrosymmetric compound Al3(IO3)9·(HIO3)6·18H2O

Single crystals of Al 3 (IO 3 ) 9 ·(HIO 3 ) 6 ·18H 2 O with sizes up to 4 × 4 × 3 mm 3 were grown by the aqua-solution method at room temperature . It crystallizes in the noncentrosymmetric (NCS) hexagonal space group P 6 3 (No. 173) with unit cell parameters of a  = 16.1149 (10) Å, c  = 12.3886 (11) Å and Z  = 2. Its structure features a 3D framework composed by the IO 3 − , HIO 3 and [Al(H 2 O) 6 ] 3+ units. It shows a powder second harmonic generation (SHG) response of about 3.5 × KDP at the particle size of 55–88 μm. The thermal stability , IR and UV–Vis–NIR diffuse reflectance spectra of Al 3 (IO 3 ) 9 ·(HIO 3 ) 6 ·18H 2 O were studied comprehensively. In addition, the first-principles calculation was carried out in order to understand the electronic structure and the origin of the linear and nonlinear optical properties .