A large variety of different interactions between the chalcogen atoms, Q, occur in the solid state structures of polyselenides and polytellurides, including both molecular and infinite units. The simplest motifs are classical Q22– dumbbells and nonlinear Qn2– chains (n = 3, 4, 5, ..), e.g. found in alkali metal polychalcogenides. In addition, nonclassical so-called hypervalent motifs exist in the form of linear Q34– units or within larger units such as Q44– and Q54–. Infinitely extended Q units include zigzag, cis/trans and linear chains, as well as planar and slightly puckered layers. Several of those are susceptible to Peierls distortions, leading to the formation of both commensurate and incommensurate superstructures and anomalies in transport properties, including metal-nonmetal transitions.

BaCu6–xSTe6 and BaCu6–xSe1–yTe6+y were synthesized from the elements at 663 K. These chalcogenides adopt a new structure type, cubic space group Pm$\bar {3}$, with a = 6.9680(2) Å in the case of BaCu5.93SeTe6. Therein, the Cu atoms form cubic clusters, centered by Se atoms, where statistically 2.07 corners are unoccupied. All Te atoms are part of Te22– dumbbells, leading to a charge‐balanced formula when x = 0: Ba2+(Cu+)6Se2–(Te22–)3. While Te atoms can be incorporated on the Se site, no evidence was found for the ability of Se atoms to replace Te in the Te22– pairs. Band structure calculations on different BaCu6SeTe6 models revealed a very small band gap at the Fermi level; all these chalcogenides with x > 0 should thus be p‐doped semiconductors, which we experimentally confirmed for BaCu5.7Se0.6Te6.4.

The chalcogenides Ba(2)Cu(4-x)Se(y)Te(5-y) were synthesized from the elements in stoichiometric ratios at 700 degrees C, followed by annealing at 600 degrees C. The ternary telluride Ba(2)Cu(4-x)Te(5) crystallizes in a new structure type, space group C2/c, with lattice dimensions of a = 9.4428(6) A, b = 9.3289(6) A, c = 13.3028(8) A, beta = 101.635(1) degrees , V = 1147.8(1) A(3), for x = 0.75(1) (Z = 4). The corresponding selenide-telluride adopts another new, but strongly related, structure type, space group P4(1)2(1)2, with a = 6.5418(3) A, c = 25.782(2) A, V = 1103.3(1) A(3), for Ba(2)Cu(3.26(2))Se(0.729(8))Te(4.271) (Z = 4). Between 0.13 and 1.0 Te per formula unit can be replaced with Se, while the Cu content appears to vary only within 0.67

No abstract

Ba(2)Cu(6-x)STe(4) and Ba(2)Cu(6-x)Se(y)Te(5-y) were prepared from the elements in stoichiometric ratios at 1123 K, followed by slow cooling. These chalcogenides are isostructural, adopting the space group Pbam (Z = 2), with lattice dimensions of a = 9.6560(6) Å, b = 14.0533(9) Å, c = 4.3524(3) Å, and V = 590.61(7) Å(3) in the case of Ba(2)Cu(5.53(3))STe(4). A significant phase width was observed in the case of Ba(2)Cu(6-x)Se(y)Te(5-y) with at least 0.17(3) ≤ x ≤ 0.57(4) and 0.48(1) ≤ y ≤ 1.92(4). The presence of either S or Se in addition to Te appears to be required for the formation of these materials. In the structure of Ba(2)Cu(6-x)STe(4), Cu-Te chains running along the c axis are interconnected via bridging S atoms to infinite layers parallel to the a,c plane. These layers alternate with the Ba atoms along the b axis. All Cu sites exhibit deficiencies of up to 26%. Depending on y in Ba(2)Cu(6-x)Se(y)Te(5-y), the bridging atom is either a Se atom or a Se/Te mixture when y ≤ 1, and the Te atoms of the Cu-Te chains are partially replaced by Se when y > 1. All atoms are in their most common oxidation states: Ba(2+), Cu(+), S(2-), Se(2-), and Te(2-). Without Cu deficiencies, these chalcogenides were computed to be small gap semiconductors; the Cu deficiencies lead to p-doped semiconducting properties, as experimentally observed on selected samples.

No abstract

New Barium Copper Chalcogenides Synthesized Using Two Different Chalcogen Atoms: Ba2Cu6-xSTe4 and Ba2Cu6-xSeyTe5-y. -Ba2Cu5.53STe4, Ba2Cu5.43Se1.92Te3.08, Ba2Cu5.64Se1.10Te3.90, and Ba2Cu5.83Se0.48Te4.52 are synthesized from the elements (silica tube, 1073 K, 48 h). The samples are characterized by single crystal XRD and LMTO electronic structure calculations. The compounds are isostructural and crystallize in the space group Pbam with Z = 2. Ba 2 Cu 6-x Se y Te 5-y shows a significant phase width with at least 0.17 ≤ x ≤ 0.57 and 0.48 ≤ y ≤ 1.92. The structure of Ba2Cu5.53STe4 contains Cu-Te chains, which are interconnected by bridging S atoms to form infinite layers alternating with Ba atoms. Without Cu deficiencies, these compounds are computed to be small gap semiconductors. Cu deficiency leads to p-doped semiconducting properties. -(MAYASREE, O.; SANKAR, C. R.; ASSOUD, A.; KLEINKE*, H.; Inorg. Chem. 50 (2011) 10, 4580-4585, http://dx.doi.org/10.1021/ic2002628 ; Dep. Chem., Univ. Waterloo, Waterloo, Ont. N2L 3G1, Can.; Eng.) -W. Pewestorf 31-018

BaCu5.72Se0.46Te6.54, BaCu5.93SeTe6, and BaCu5.92S0.986Te6.014 are synthesized from the elements (silica tubes, 663 K, 240 h) and characterized by single crystal XRD and DFT-based LMTO electronic band structure calculations. The compounds crystallize in the cubic space group Pm3 with Z = 1 in a hitherto unknown structure type comprising chalcogen-centered Cu atom clusters and dumbbells, while the Ba atoms are encapsulated in pentagonal Cu8Te12 dodecahedra. BaCu5.7Se0.6Te6.4 is a p-type semiconductor with moderate thermoelectric figure of merit, resulting from a combination of high Seebeck coefficient, low thermal conductivity, and low electrical conductivity. -(MAYASREE, O.; SANKAR, C. R.; CUI, Y.; ASSOUD, A.; KLEINKE*, H.; Eur. J. Inorg. Chem. 2011, 26, 4037-4042, http://dx.