Rare-Earth Substitution Induced Symmetry Breaking for The First Sc-Based Nonlinear Optical Chalcogenide with High-Performance

Chalcogenides are the most important infrared nonlinear optical (NLO) material candidates, and the exploration of high-performance ones is attractive and challengeable. Hitherto, there is no NLO scandium (Sc) chalcogenides experimentally studied. Here, new quaternary Sc thiophosphate CsScP 2 S 7 (CSPS) was synthesized by the facile metal oxide-boron-sulfur/reactive flux hybrid solid-state method. It crystallizes in the monoclinic chiral space group C 2, and the layered structure is composed by the new ScP 2 S 11 functional motifs built by ScS 6 octahedra and P 2 S 7 dimers, and the structure-performance analysis reveals that the hyperpolarizability of ScP 2 S 11 is much greater than the assembled units (ScS 6 and PS 4 ), which makes the first NLO Sc chalcogenide CSPS exhibits strong NLO response (0.8 × AGS) and high laser-induced damage threshold (LIDT) (4.3 × AGS), and a wide bandgap of 3.10 eV. With the coordination number's reduction of rare-earth (RE) ion and the rearrangement of P 2 S 7 dimers, the centrosymmetric structure of CsREP 2 S 7 family can be broken via substitution with the smallest RE element Sc to form the noncentrosymmetric structure. This work not only discovers a new high-performance infrared NLO material, but also will inspire researchers to explore more potential NLO Sc chalcogenides.