Snpq(3) (Q = S, Se, S/Se): A Series Of Lone-Pair Cationic Chalcogenophosphates Exhibiting Balanced Nlo Activity Originating From Snq(8) Units

Two chalcogenophosphates, SnPS2.86Se0.14 (1) and SnPSe3 ( 2), are isostructural and crystallize in the monoclinic noncentrosymmetric space group Pn. Their three-dimensional (3D) structures are constructed by [Sn(1)Q(8)] hendecahedra and [Sn(2)Q(8)] dodecahedra by sharing Q vertices and edges, leaving cavities for isolated [P(2)Q(6)] (Q = S/Se, Se) dimers. A secondharmonic-generation (SHG) measurement indicates that 1 is phase-matchable with a response of approximately 1.2 x AgGaS2 (AGS), which is verified by the theoretical calculation result. The powder sample of 1 exhibits a high laser-induced damage threshold of 3.9 x AGS. For comparison, the known SnPS3 (3) was also synthesized and evaluated using the same method. The chemical composition-NLO performance relationship of 1-3 is also discussed. Dipole moment calculation results suggest that [SnQ(8)] polyhedra make the main contribution to their excellent nonlinear optical (NLO) performance.