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

Abstract

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 D2h16–Pnma of the orthorhombic system. The structure features ∞1[MAnTe74–] strips (M = Cr or Ti; An = Th or U) that propagate in the b-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[MAnTe74–] 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.

Modulated Linear Tellurium Chains in Ba3ScTe5: Synthesis, Crystal Structure, Optical and Resistivity Studies, and Electronic Structure

“…Å (Figure 3b). An = Th, U), 65 KTh2Te6, 66 BaAnTe4 (An = Th and U), 67 and ATiU3Te9 (A = Rb and Cs). 68 The assignments of +2 and +3 oxidation states to Ba and Sc atoms, respectively are clear Optical Band Gap Study.…”

“…Assignment of the formal oxidation states in the Ba 3 ScTe 5 substructure is not straightforward because of the presence of Te···Te···Te infinite chains with Te···Te interactions that are shorter than the van der Waals distance and longer than the typical Te–Te single bond (∼2.8 Å). There are numerous examples of metal tellurides where assignment of the oxidation states of Te atoms is complicated and somewhat arbitrary because of such intermediate Te···Te interactions, e.g., LnTe 3 (Ln = lanthanides), LnCu x Te 2 (Ln = La, Nd, Sm, Gd, and Dy), Gd 3 Cu 2 Te 7 , Ba 2 MAnTe 7 (M = Ti and Cr; An = Th and U), KTh 2 Te 6 , BaAnTe 4 (An = Th and U), and ATiU 3 Te 9 (A = Rb and Cs) …”

“…Hence, we conclude that the presence of these distorted chains of Te with an average charge of −1.5 e − per Te atom is responsible for stabilization of Ba3ScTe5 in the Hf5Sn3Cu structure type.Thus, based on the coordination environments and the distances between the homo/hetero atoms, charge balance in the valence-imprecise Ba3ScTe5 structure can be formulated as (Ba 2+ )3(Sc 3+ )(Te 2− )3(Te 1.5− )2. An average charge of −1.5 e − on the Te atoms of the infinite atoms of Te•••Te•••Te chains is common and is reported for many of the tellurides including the Ba2MAnTe7 (M = Ti, Cr, An = Th, U)65 , CuxUTe3,71 and ATiU3Te9 structures 68.…”

Synthesis, crystal structure, optical, and electronic study of the new ternary thorium selenide Ba3ThSe3(Se2)2

“…The few known quaternary thorium chalcogenides include ACuThQ 3 (A = K, Cs, Tl; Q = S, Se) [23][24][25][26], Ba 2 Cu 2 ThS 5 [27], Ba 2 Cu 2 ThSe 5 [28], K 2 Cu 2 ThS 4 [23], K 3 Cu 3 Th 2 S 7 [23], KThSb 2 Se 6 [29], and Ba 2 CrThTe 7 [30].…”

Synthesis, crystal structure, resistivity, and electronic structure of the U(V) quaternary polyselenide Ba8PdU2Se12(Se2)2

“…There are relatively few quaternary actinide chalcogenides with [16], Ak 2 Cu 2 AnQ 5 (Ak ¼ Ba, Sr; An¼Th, U; Q ¼S, Se) [16][17][18], CsUMTe 5 (M ¼Ti [19] and Zr [20]), ATiU 3 Te 9 (A ¼Rb, Cs) [21], Cs 5 Hf 5 UTe 30.6 [19], Ba 2 MAnTe 7 (M ¼Ti, Cr; An¼Th, U) [22], and AMUQ 3 (A ¼Rb, Cs) [23]. The chemistry of these uranium chalcogenides is dominated by U 4 þ compounds.…”