Synthesis, crystal structures and nonlinear optical properties of beta-RbCdI3 center dot H2O and CsCdI3 center dot H2O

摘要

Searching for new IR nonlinear optical (NLO) crystals with a high laser damage threshold (LDT) is still a challenge. In this paper, two new halides, -RbCdI3H2O and CsCdI3H2O, have been synthesized by a conventional solution reaction. Both of them crystallize in the monoclinic space group Pc (no. 7). In their crystal structures, all the corner-sharing [CdI4] tetrahedra connect with each other to form 1D chains, which further connect with [Rb(H2O)](+)/[Cs(H2O)](+) complexes to form three-dimensional (3D) frameworks. All the polar [CdI4](2-) groups align in such a way that results in a favorable net polarization. Powder second-harmonic generation (SHG) measurements indicate that -RbCdI3H2O and CsCdI3H2O show phase-matchable SHG responses of 2.7 and 2.6 times that of KH2PO4 (KDP). The infrared transmission range can reach 21 m. The UV-vis diffuse reflectance spectra indicate that the band gaps of -RbCdI3H2O and CsCdI3H2O are about 3.26 and 3.54 eV, respectively. A preliminary measurement indicates that the LDT of their powders is about 90 and 100 MW cm(-2), respectively, suggesting that -RbCdI3H2O and CsCdI3H2O are two new promising IR NLO materials. Their band structure and optical property calculations based on DFT methods are carried out.