Noncentrosymmetric Inorganic Open-Framework Chalcohalides with Strong Middle IR SHG and Red Emission: Ba3AGa5Se10Cl2 (A = Cs, Rb, K)

Novel SHG effective inorganic open-framework chalcohalides, Ba3AGa5Se10Cl2 (A = Cs, Rb and K), have been synthesized by high temperature solid state reactions. These compounds crystallize in the tetragonal space group I4̅ (No.82) with a = b = 8.7348(6) – 8.6341(7) Å, c = 15.697(3) – 15.644(2) Å, V = 1197.6(3) – 1166.2(2) Å3 on going from Cs to K. The polar framework of 3∞[Ga5Se10]5– is constructed by nonpolar GaSe45– tetrahedron (T1) and polar supertetrahedral cluster Ga4Se108– (T2) in a zinc-blende topological structure with Ba/A cations and Cl anions residing in the tunnels. Remarkably, Ba3CsGa5Se10Cl2 exhibits the strongest intensity at 2.05 μm (about 100 times that of the benchmark AgGaS2 in the particle size of 30–46 μm) among chalcogenides, halides, and chalcohalides. Furthermore, these compounds are also the first open-framework compounds with red photoluminescent emissions. The Vienna ab initio theoretical studies analyze electronic structures and linear and nonlinear optical properties.