Partial congener substitution induced centrosymmetric to noncentrosymmetric structural transformation and nonlinear optical properties of PbSnSiS4

Abstract

The PbxSn2−xSiS4 series from 0 ≤ x ≤ 2 were investigated to study the influence of partial congener cationic substitution on structure and properties. While the centrosymmetric (CS) compounds Pb2SiS4 and Sn2SiS4 crystallizing in the centrosymmetric (CS) P21/c space group have been reported previously, the partial congener cationic substitution induced CS to noncentrosymmetric (NCS) structural transformation in this system and the formed NCS substitution variant PbSnSiS4 are introduced here for the first time. PbSnSiS4 crystallizes in P21 space group with the cell parameters a = 6.4334(8) Å; b = 6.6912(8) Å, c = 8.5037(10) Å, β = 108.576(4) °, Z = 2. The title compound shows a strong second harmonic generation (SHG) response (~ 1.1 × AgGaS2), high laser induced damage threshold (LIDT) (~3 × AgGaS2), and wide IR transparent region from 0.58 to 16.85 µm (down to zero). What’s more, PbSnSiS4 exhibits good crystal growth habits, and millimeter-scale single crystals (~ 2 × 2 × 1 mm3) were obtained in a spontaneous crystallization way. The theoretical calculations indicate that the optical band gaps decrease with increasing Sn content from Pb2SiS4 (1.94 eV), PbSnSiS4 (1.82 eV), to Sn2SiS4 (1.69 eV). The results give an insight into the exploration of new NCS compounds with the congener cationic substitution strategy.