Structure-property survey and computer-assisted screening of mid-infrared nonlinear optical chalcohalides

The chalcohalides which feature the mix of sulfur and halogen in a non-centrosymmetric coordinated environment can induce mid-infrared (IR) nonlinear optical (NLO) performance. Compared with traditional chalcogenides, the development and exploration of chalcohalides in the mid-IR NLO field have not been received systematic research and attention. In this review, the high-throughput screening of non-centrosymmetric chalcohalides is carried out, and the structures and optical properties of the chalcohalides are summarized and investigated. The results indicate that the chalcohalides would be potential applications in mid-IR NLO materials. Introduction of the halogen atoms with a large electronegativity into chalcogenides will increase their band gaps, and the coordination polyhedra could be more distorted owing to the difference of bond length which is beneficial to large second harmonic generation (SHG) responses. The transition metal chalcohalides exhibit strong SHG responses when the asymmetric units with large distortion are aligned uniformly. The adduct-type chalcohalides and Lewis acid adduct chalcohalides that contain novel isolated rings can have large birefringence. In particularly, a series of alkali metal chalcohalides are highlighted owing to their good mid-IR NLO properties involving wide band gaps and large NLO coefficients. All the results suggest that the chalcohalides are potential systems in exploring new mid-IR materials. (C) 2020 Elsevier B.V. All rights reserved.