Two Phosphates: Noncentrosymmetric Cs₆Mg₆(PO₃)₁₈ and Centrosymmetric Cs₂MgZn₂(P₂O₇)₂

Two new phosphates—Cs 6 Mg 6 (PO 3 ) 18 (CMP) and Cs 2 MgZn 2 (P 2 O 7 ) 2 (CMZP)—have been obtained, using high-temperature molten methods. Crystals of CMP with the polar P 2 1 space group display a new three-dimensional (3D) anionic framework possessing two one-dimensional (1D) [PO 3 ] ∞ chains that are interconnected by isolated MgO 6 octahedra, while CMZP with centrosymmetric monoclinic space group P 2 1 / c possesses a new [MgZn 2 P 4 O 20 ] 14– structure unit consisting of two isolated P 2 O 7 dimers, one ZnO 4, and two disordered Mg/ZnO 4 tetrahedral units. The polar phosphate CMP with deep-UV transparency (below 190 nm) shows weak second harmonic generation (SHG) response (0.1 × KDP), and the dipole moment analysis suggests that the weak SHG response mostly originates from much distorted CsO n polyhedron. Some related properties, such as optics, thermostability, and band structure derived from density functional theory, were explored.