New iodate fluoride Rb2Ce(IO3)5F with nonlinear optical properties

Abstract

New noncentrosymmetric cerium(IV) iodate fluoride Rb₂Ce(IO₃)₅F was prepared employing a hydrothermal technique. The compound crystallizes in the Cmc2₁ 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 Rb₂Ce(IO₃)₅F consists of layers composed of 8-vertex CeO₇F and 7-vertex Rb(1)O₇ and Rb(2)O₆F polyhedra interconnected by I(2)O₃ groups. These layers are stitched by trigonal pyramidal I(1)O₃ and I(3)O₃ groups into a 3D framework. Synthesized iodate fluoride is thermally stable in air up to 430 °C. According to DFT calculations, Rb₂Ce(IO₃)₅F 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 Rb₂Ce(IO₃)₅F is the ability to generate a second optical harmonic signal comparable to that of KH₂PO₄.