Partial congener substitution induced centrosymmetric to noncentrosymmetric structural transformation and nonlinear optical properties of PbSnSiS4
The Pb x Sn 2−x SiS 4 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 Pb 2 SiS 4 and Sn 2 SiS 4 crystallizing in the centrosymmetric (CS) P 2 1 / 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 PbSnSiS 4 are introduced here for the first time. PbSnSiS 4 crystallizes in P 2 1 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 × AgGaS 2 ), high laser induced damage threshold (LIDT) (~3 × AgGaS 2 ), and wide IR transparent region from 0.58 to 16.85 µm (down to zero). What’s more, PbSnSiS 4 exhibits good crystal growth habits, and millimeter-scale single crystals (~ 2 × 2 × 1 mm 3 ) were obtained in a spontaneous crystallization way. The theoretical calculations indicate that the optical band gaps decrease with increasing Sn content from Pb 2 SiS 4 (1.94 eV), PbSnSiS 4 (1.82 eV), to Sn 2 SiS 4 (1.69 eV). The results give an insight into the exploration of new NCS compounds with the congener cationic substitution strategy.
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