Synthesen und Kristallstrukturen von neuen Alkalimetall‐Selten‐Erd‐Telluriden der Zusammensetzungen KLnTe₂ (Ln = La, Pr, Nd, Gd), RbLnTe₂ (Ln = Ce, Nd) und CsLnTe₂ (Ln = Nd)

Abstract

Von den Verbindungen der Zusammensetzung ALnQ2 (A = Na, K, Rb, Cs; Ln = Selten‐Erd‐Metall; Q = S, Se, Te) konnten die Kristallstrukturen der neuen Telluride KLaTe2, KPrTe2, KNdTe2, KGdTe2, RbCeTe2, RbNdTe2 und CsNdTe2 durch Einkristallröntgenstrukturanalysen bestimmt werden. Sie kristallisieren allesamt im α‐NaFeO2‐Typ mit der Raumgruppe R3¯m und drei Formeleinheiten in der Elementarzelle. Die Gitterparameter lauten: KLaTe2: a = 466, 63(3) pm, c = 2441, 1(3) pm; KPrTe2: a = 459, 73(2) pm, c = 2439, 8(1) pm; KNdTe2: a = 457, 83(3) pm, c = 2443, 9(2) pm; KGdTe2: a = 449, 71(2) pm, c = 2443, 3(1) pm; RbCeTe2: a = 465, 18(2) pm, c = 2533, 6(2) pm; RbNdTe2: a = 459, 80(3) pm, c = 2536, 5(2) pm und CsNdTe2: a = 461, 42(3) pm, c = 2553, 9(3) pm. Kennzeichnend für den Aufbau des α‐NaFeO2‐Strukturtyps als geordnete Substitutionsvariante des NaCl‐Typs sind Schichten aus kantenverknüpften [(A+/Ln3+)(Te2—)6]‐Oktaedern, in denen die Besetzung durch die Kationen A+ und Ln3+ schichtweise alterniert.

Diverse Closed Cavities in Condensed Rare Earth Metal–Chalcogenide Matrixes: Cs[Lu7Q11] and (ClCs6)[RE21Q34] (RE = Dy, Ho; Q = S, Se, Te)

“…The major A/RE/Q structure types have been shown in Figure , which has nicely displayed a correlation between the structure and the A/RE atomic ratio. As discussed briefly in the Introduction, as the A/RE atomic ratio increases from 0.14 (Cs[Lu 7 Q 11 ]) to 1 (AREQ 2 type − ), the structure varies from a closed cavity structure to an open channel structure and then to a 2D layered structure. Such a trend goes roughly monotonically with the density decrease (identity of atom should be taken into account).…”

“…Ternary alkali metal/rare earth metal/chalcogenide compounds (A/RE/Q, Q = S, Se, Te) are fascinating for their complexity and beauty. Up until now, eight types of structures are known and are listed according to their A/RE/Q stoichiometries as following, 1:1:2 (including about 40 compounds, e.g., RbLaSe 2 ), − 3:7:12 (adopted by roughly 10 compounds, e.g., Rb 3 Yb 7 Se 12 ), − 1:3:5 (only 2 examples of CsEr 3 Se 5 and CsHo 3 Te 5 ), 3:11:18 (only found in Cs 3 Tm 11 Te 18 ), 1:5:8 (RbSc 5 Te 8 ), 2:24:36 (as found in a Tm fractional occupied example, K 2 Tm 23.33 S 36 ), 1:1:4 (including 12 compounds, e.g., KCeSe 4 ), − and 1:3:8 (including 4 compounds, e.g., KPr 3 Te 8 ). ,, Note that 1:1:4 and 1:3:8 types of compounds possess Q–Q bonding interactions and are thus excluded from the structure discussion below. Another exception is K 2 Tm 23.33 S 33 in which two types of building units are found as TmS 6 and TmS 7 .…”

Synthesis, Structure, Magnetism, and Optical Properties of Cs2Cu3DyTe4

“…The cesium cations residing between the layers are 7-fold coordinated in a monocapped trigonal prism with Cs–Te bond lengths between 3.75 and 3.92 Å, which are somewhat shorter than those of 3.90–4.21 Å in CsCu 3 Sc 3 Te 6 or 3.81–4.34 Å in CsCuGd 2 Te 4 . However, the coordination number might justify these bond lengths as seen in layered CsNdTe 2 (Cs–Te = 3.78 Å; CN(Cs) = 6), CsZnNdTe 3 (Cs–Te ranged from 3.79 to 4.19 Å; CN(Cs) = 8), and CsBi 4 Te 6 (Cs–Te from 3.76 to 4.19 Å; CN(Cs) = 10) or in the three-dimensional Cs 0.73 Cu 5.27 Pr 2 Te 6 (Cs2–Te = 3.69 Å; CN(Cs) = 6) . The Cs···Cu contact at 3.84 Å is relatively short but not unusual, as similar ones at 3.79 Å have been reported in CsCu 3 Dy 2 Se 5 , for example.…”

LaTe1.82(1): modulated crystal structure and chemical bonding of a chalcogen-deficient rare earth metal polytelluride

“…These Te 3 2À anions are, however, more or less isolated in the structures and no interactions amongst them or with other anionic fragments are expected. Bent Te 3 entities with Te-Te-Te angles close to 90 were described as parts of the anionic substructure in disordered polytellurides like KRE 3 Te 8 (Stö we et al, 2003;Patschke et al, 1998) and RbUSb 0.33 Te 6 (Choi & Kanatzidis, 2001), and in the modulated structures of K 1/3 Ba 2/3 AgTe 2 (Gourdon et al, 2000), LnTe 3 (Malliakas et al, 2005) and RESeTe 2 (Fokwa et al, 2002;Fokwa Tsinde & Doert, 2005), for example.…”