BaSi_(7)P_(10) and SrSi_7P_(10): Two Infrared Nonlinear Optical Phosphides with T2 Supertetrahedra Exhibiting Strong Second-Harmonic Generation Effects

摘要

Because mid- and far-infrared (IR) nonlinear optical (NLO) materials playan important role in military and civil fields, plenty of excellent IR NLOmaterials have been discovered in recent decades, such as chalcogenideswith T2 supertetrahedra. Pnictides with T2 supertetrahedra instead of MQ_4(M = ⅡB, ⅢA, ⅣA metals; Q = P, As) tetrahedra, may favor high secondharmonicgeneration (SHG) efficiency due to their large hyperpolarizability,but they have been rarely reported. Therefore, in this study, two pnictideswith T2 supertetrahedra, BaSi_7P_（10） and SrSi_7P_（10）, are synthesized and studied.With three-dimensional (3D) framework structures assembled from 1D zigzagchains of [Si_7P_（16）] dual-T2 supertetrahedra, both BaSi_7P_（10） and SrSi_7P_（10） exhibitstrong phase-matching (PM) SHG responses (3.2- and 3.0-times that ofAgGaS_2), large birefringences (0.077 and 0.112), and wide infrared transparency.In addition, theoretical calculation also reveals that the two-coordinatedP atom can enhance the SHG effects. This study provides a new strategy forexploring new IR NLO materials.