Cs3VO(O-2)(2)CO3: an exceptionally thermostable carbonatoperoxovanadate with an extremely large second-harmonic generation response

A novel nonlinear optical (NLO) carbonatoperoxovanadate, Cs3VO(O-2)(2)CO3, with an exceptionally high thermostability was successfully synthesized by introducing highly polarizable Cs+ cations and inorganic polydentate carbonate anions into asymmetric peroxovanadates. The structure of Cs3VO(O-2)(2)CO3 is composed of distorted [VO(O-2)(2)CO3](3-) units and charge balancing Cs+ cations. The title compound exhibits the largest NLO intensity ever found in the current carbonate NLO materials, i.e., 23.0 times that of KH2PO4 (KDP). The remarkably strong second-harmonic generation (SHG) response originates from the synergistic effect of the exceedingly polarizable Cs+ cations, distortive polyhedra of the V5+ cation, delocalized orbitals in CO3 groups, and distorted localized orbitals in O-2 groups. First-principles calculations indicated that introducing the polarizable cations into peroxovanadates not only induces the enhancement of the SHG response but also improves the thermal stability of the framework.