来源：ACS Publications
Rare-earth (RE) chalcogenides have been extensively studied as infrared nonlinear optical (NLO) materials and have become promising candidates for achieving good integrated performance; however, the subgroup RE chalcophosphates have been rarely studied, especially Y-based ones. Here, a new quaternary RE selenophosphate, Cs2YP2Se7 (1), and the first NLO-active Y-based selenophosphate, KYP2Se6 (2), were synthesized via the reactive flux AI (A = K, Cs) assisted RExOy–B–Se solid state method developed by us. They crystallize in the monoclinic P21/n and orthorhombic chiral P212121 structure, respectively. The structure of 1, featuring {[Y2P4Se14]4–}∞ layers constructed by YSe6, PSe4 and P2Se6 units, transforms to the structure of 2, constructed from {[YP2Se6]−}∞ layers built by YSe8 and P2Se6 units under the size effect of A+ cations. The symmetry breaking enables second-harmonic generation (SHG) response in 2, and theoretical calculations reveal that the synergistic effect between YSe8 and P2Se6 units contributes to the SHG activity.