New layered nonlinear optical iodate Cs₃Ta(IO₃)₈: topology-symmetry analysis and structure prediction

New polar iodate Cs3Ta(IO3)(8), space group P31c, has been obtained under mild hydrothermal conditions and its structural determination was carried out with a single crystal. Two types of layers were selected and characterized using topology and symmetry analysis. The structure of the new iodate has relation with KSc(IO3)(3)Cl determined earlier. The polar space group corresponds to the presence of the distinct effect of optical second harmonic generation, but the SHG intensity is limited due to lack of phase matching for neodymium laser radiation and its second harmonic. The low optical nonlinearity is consistent with the structural feature of the crystal, and the polarity is determined mainly by the positions of Cs cations with a slight deviation from the centrosymmetry of the entire structure as a whole. Two structural variants of Cs3Ta(IO3)(8) are predicted based on a OD topology-symmetry approach.