Cation Equivalent Multisubstitution Realizing Structure Transformation and Balanced Nonlinear Optical Performance of Quaternary Eu-Based Chalcogenides.

Rare-earth (RE) elements play an important role in constructing nonlinear optical (NLO) materials in view of their capability of creating acentric coordination polyhedra with anions. Here, two new RE chalcogenides EuCdSnQ (Q = S (), Se ()) were successfully synthesized by the facile metal oxide-boron-chalcogen/reactive flux hybrid solid-state method by taking EuZnGeS () as the parent via two-site equivalent cosubstitution. They crystallize with the orthorhombic noncentrosymmetric space group 2, different from the centrosymmetric structure of . The structural evolution from to and is elucidated in detail. The structures of and feature {[CdSnQ]} layers assembled by {[CdSnQ]} chains and [CdSnQ] quadrilaterals. They both show phase matchable NLO responses of 0.6 () and 0.8 () × AGS. Theoretical calculations and structural analysis indicate that their good NLO performances are mainly contributed by the [EuQ] bicapped trigonal prisms. This work enriches the study of RE-based NLO materials.