Cation and anion co-partial substitution induced centrosymmetric to noncentrosymmetric structural transformation to construct nonlinear-optical rare-earth oxythiogermanates

M x Eu 18− x Ge 9 O 5 S 31 ( R 3) were obtained by cationic and anionic co-partial substitution of β-Eu 2 GeS 4 ( P 2 1 / m ), which induced centrosymmetric to noncentrosymmetric structural transformation and balanced second-order nonlinear optical activity.