New iodate fluoride Rb 2 Ce(IO 3 ) 5 F with nonlinear optical properties.

New noncentrosymmetric cerium(IV) iodate fluoride Rb 2 Ce(IO 3 ) 5 F was prepared employing a hydrothermal technique. The compound crystallizes in the Cmc 2 1 space group (#36) with cell parameters a = 11.1518(6) Å, b = 8.1187(4) Å and c = 17.1581(10) Å. The crystal structure of Rb 2 Ce(IO 3 ) 5 F consists of layers composed of 8-vertex CeO 7 F and 7-vertex Rb(1)O 7 and Rb(2)O 6 F polyhedra interconnected by I(2)O 3 groups. These layers are stitched by trigonal pyramidal I(1)O 3 and I(3)O 3 groups into a 3D framework. Synthesized iodate fluoride is thermally stable in air up to 430 °C. According to DFT calculations, Rb 2 Ce(IO 3 ) 5 F is a direct-gap semiconductor with a band gap of ca. 2.33 eV. This value is in good agreement with an estimated optical gap value of 2.35 eV. The important feature of Rb 2 Ce(IO 3 ) 5 F is the ability to generate a second optical harmonic signal comparable to that of KH 2 PO 4 .