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

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