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 VO(O ) CO , 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 VO(O ) CO is composed of distorted [VO(O ) CO ] units and charge balancing Cs cations. The title compound exhibits the largest NLO intensity ever found in the current carbonate NLO materials, e., 23.0 times that of KH PO (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 cation, delocalized π orbitals in CO groups, and distorted localized π orbitals in O 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.