Synthesis, structure and optical properties of two isotypic crystals, Na3MO4Cl (M=W, Mo)

Abstract

Two isotypic compounds, Na3MO4Cl (M = W, Mo) have been obtained from the high temperature solution, and their structures were determined by single-crystal X-ray diffraction. Both of them crystallize in the space group P4/nmm of tetragonal system with the unit cells: a=7.5181(15), c=5.360(2) for Na3WO4Cl and a=7.4942(12), c=5.3409(18) for Na3MoO4Cl. The structure exhibits a 3D network built up by the ClNa6 groups, and the MO4 groups reside in the tunnels of the 3D network. The structural similarities and differences between Na3MO4Cl (M=W, Mo) and Sr3MO4F (M=Al, Ga) have been discussed. Meanwhile, detailed structure comparison analyses between Na3MO4Cl (M=W, Mo) and Na3MO4F (M=W, Mo) indicate that the different connection modes of ClNa6 and FNa6 make Na3MO4Cl and Na3MO4F crystallize in different structures. The IR spectra were used to verify the validity of the structure. The diffuse reflectance spectra show that the UV absorption edges are about 249nm (4.99eV) and 265nm (4.69eV) for Na3WO4Cl and Na3MoO4Cl, respectively. In addition, the first-principles theoretical studies are also carried out to aid the understanding of electronic structures and linear optical properties.