Die Kristallstrukturen von α‐Na₂S₂ und K₂S₂, β‐Na₂S₂ und Na₂Se₂

Abstract

α‐Na2S2 (a = 7,629 Å; c = 5,394 Å) und K2S2 (a = 8,49 Å; c = 5,84 Å) kristallisieren hexagonal in der Raumgruppe D 3h3—P62m mit 3 Formeleinheiten pro Zelle. Sie sind isotyp mit Na2O2. β‐Na2S2 (a = 4,494 Å; c = 10,228 Å) und Na2Se2 (a = 4,685 Å; c = 10,53 Å) kristallisieren hexagonal in der Raumgruppe D 6h4—P63/mmc mit 2 Formeleinheiten pro Zelle. Sie sind isotyp mit Li2O2. Charakteristisch für alle vier Kristallstrukturen ist das Auftreten von S 22−‐Hanteln, die parallel der c‐Achse angeordnet sind. Der SS‐(SeSe)‐Abstand beträgt 2,13 Å (2,38 Å). Die Strukturuntersuchungen wurden mit Hilfe von Drehkristall‐ und Pulveraufnahmen durchgeführt.

Solid State Polyselenides and Polytellurides: A Large Variety of Se–Se and Te–Te Interactions

“…The simplest polychalcogenide motif is the dumbbell unit Q 2 2– , occurring for example in Na 2 Se 2 [26], Rb 2 Se 2 and Rb 2 Te 2 with Se–Se and Te–Te distances of 2.38 Å, 2.47 Å and 2.78 Å, respectively (Figure 1). These dumbbells are also found in organic compounds with similar bond lengths, e.g.…”

First-Principles Study on Structural and Electronic Properties of α-S and Na–S Crystals

“…Experimental lattice parameters and atomic positions have been reported for the Na-S crystals. [40][41][42][43][44][45] Table II shows lattice constants and Wycoff atomic positions fully-optimized by PBE calculations and experimental values for orthorhombic Na 2 S 5 (space group Pnma), tetragonal Na 2 S 4 (I " 42d), hexagonal ¡-Na 2 S 2 (P " 62m), hexagonal ¢-Na 2 S 2 (P6 3 =mmc), and cubic Na 2 S (Fm " 3m), respectively. All the lattice constants calculated by PBE agree well with the experiments, overestimating within the range from +0.2 to +1.9%.…”

The crystal structure of sodium tetrasulphide, Na2S4

“…The many analogous M2S,, compounds form an interesting area for systematic studies of sulphur-sulphur bonds in structures with different M and S,, species. Of about fifteen polysulphides described in the literature the crystal structures have been determined for only NazS2, KES2 (obtained from powder data) by F6ppl, Busmann & Frorath (1962) and CszS6 (obtained from single-crystal data) by Abrahams & Grison (1953) and Hordvik & Sletten (1968). The surprisingly few structure determinations that have been performed probably reflect the difficulties in single-crystal preparations of polysulphides.…”