Two new barium indium phosphates with intersecting tunnel structures: BaIn2P4O14, and Ba3In2P4O16

Two new barium indium phosphates BaIn2P4O14 and Ba3In2P4O16 were synthesized by high temperature solution growth method and structurally characterized by single crystal X-ray diffraction analysis. They represent first compounds in the Ba–In–P–O systems. BaIn2P4O14 and Ba3In2P4O16 display different types of 3D architectures. The projections of both structures concern about the existence of the intersecting tunnels. In compound BaIn2P4O14, the tunnels are built up of the corner-sharing InO6 octahedra and P2O7 groups, whereas in compound Ba3In2P4O16, they are formed by corner sharing of PO4 tetrahedra and InO6 octahedra. The electronic band structure calculations of two compounds have been performed with the density functional theory method. The study of calculations and optical diffuse reflectance experimental results show both compounds are insulators with direct band-gap.