Cs(3)VO(O(2))(2)CO(3): an exceptionally thermostable carbonatoperoxovanadate with an extremely large second-harmonic generation response

A novel nonlinear optical (NLO) carbonatoperoxovanadate, Cs(3)VO(O(2))(2)CO(3), 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 Cs(3)VO(O(2))(2)CO(3) is composed of distorted [VO(O(2))(2)CO(3)](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 KH(2)PO(4) (KDP). The remarkably strong second-harmonic generation (SHG) response originates from the synergistic effect of the exceedingly polarizable Cs(+) cations, distortive polyhedra of the V(5+) cation, delocalized π orbitals in CO(3) groups, and distorted localized π 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.