Ce-based polar materials are promising NLO candidates due to their unique electronic configuration of Xe 4f15d16s2 and diverse coordination modes. Ce4+ compounds are highly desired candidates for advanced nonlinear optical materials, yet the development of trivalent cerium-based NLO materials exhibiting a high second-harmonic-generation (SHG) response (above 3.0 × KDP) remains a great challenge. Herein, a new cerium iodate, Ce2(IO3)6(H2O), crystallized in the polar space group Pn (No. 7), was discovered by introducing rare-earth cations into iodates with a hydrothermal method, where corner-shared distorted CeO9 polyhedra and IO3- groups alternately connect to assemble a three-dimensional (3D) framework. Optical studies showed that Ce2(IO3)6(H2O) exhibits strong SHG intensities (3 × KDP), a large band gap of 2.83 eV in the trivalent Ce-based NLO materials, indicating its potential application in frequency conversion. First-principles simulations of Ce2(IO3)6(H2O) were conducted to investigate the molecular structure and optical properties. First-principles calculations, informed by structural analysis, indicate that the two kinds of polarizable cerium-centered polyhedra (Ce(1)O9 and Ce(2)O8(H2O)) constitute the primary contribution to the SHG coefficients.
Liu et al. (Mon,) studied this question.