Three New Quaternary Actinide Chalcogenides Ba₂TiUTe₇, Ba₂CrUTe₇, and Ba₂CrThTe₇: Syntheses, Crystal Structures, Transport Properties, and Theoretical Studies

The three new quaternary actinide chalcogenides Ba₂TiUTe₇, Ba₂CrUTe₇, and Ba₂CrThTe₇ have been synthesized. From single-crystal X-ray diffraction studies these isostructural compounds are found to crystallize in a new structure type in space group <i>D</i>_2<i>h</i>¹⁶–<i>Pnma</i> of the orthorhombic system. The structure features _∞¹[MAnTe₇^4–] strips (M = Cr or Ti; An = Th or U) that propagate in the <i>b-</i>direction and are separated by Ba cations. An atoms are coordinated to eight Te atoms in a bicapped trigonal-prismatic geometry while M atoms are octahedrally coordinated to six Te atoms. Sharing of the AnTe₈ and MTe₆ polyhedra forms _∞¹[MAnTe₇^4–] strips. The presence of the infinite linear Te–Te–Te chains in these compounds makes assignment of oxidation states arbitrary. Resistivity measurements and DFT calculations provide further insight into the properties of these compounds