Solid-State Preparation, Structural Characterization, Physical Properties, and Theoretical Studies of a Series of Novel Rare-Earth Metal Chalcogenides with Unprecedented Closed-Cavities

Multinary rare-earth metal chalcogenides have aroused great concern owing to their special structure characteristics and diverse physical functions. In this work, five novel rare-earth chalcogenides adopt the formula Cs-2[RE8InS14] (where RE = Ho-Lu), obtained by the elemental mixture in CsCl flux at 1273 K. They are isotype and belong to orthorhombic Cmca (no. 64) [a = 15.711(7)-15.385(2) angstrom, b = 22.232(2)-21.786(2) angstrom, c = 15.483(5)-15.244(2) angstrom, V = 5408.4(4)-5130.1(7) angstrom(3) and Z = 8], exhibiting a dense 3D [RE8InS14] framework consisting of RES6 octahedron and discrete InS4 tetrahedron. The large closed-cavities of Cs-4@S-26 are far apart and embedded within the network along bc-plane, which was discovered for the first time. The band gaps from 2.45 to 2.72 eV for Cs-2[RE8InS14] were deduced from the UV-Vis-NIR spectroscopy based on the Kubelka-Munk function. A magnetic test indicates that the Cs-2[RE8InS14] (RE = Ho-Yb) compounds possess paramagnetism above 50 K. In addition, the solid-state preparation, structural characterization, and theoretical studies together with a structure-G/H ratio relationship (G = atomic number of guest metals; H = atomic number of host metals) are also presented.