Solid state polyselenides and polytellurides: a large variety of Se-Se and Te-Te interactions

Abstract

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 Q(2)(2-) dumbbells and nonlinear Q(n)(2-) 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 Q(3)(4-) units or within larger units such as Q(4)(4-) and Q(5)(4-). 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.

Figure 1

From left to right: Oligomeric Q_n^2– motifs in Na₂Se₂, K₂Se₃, Na₂Se₄, and K₂Se₅.

Figure 2

Oligomeric Te_n^2– motifs in (NEt₄)₂Te₁₂ (left) and Cs₂Te₁₃ (right).

Figure 3

From left to right: Se₃^4– (D_∞h), Se₃^4– (C_2v), Se₄^4–, cis-Se₅^4– and trans-Te₅^4–.

Figure 4

Infinite Te^1– chains in Ca_0.5K₄Te₃ (left) and K₅Te₃ (right).

Figure 5

Peierls distortion of a linear ${}_{\infty }{}^1[$ Te^–] chain.

Figure 6

Various Te atom chains of TlTe.

Figure 7

Infinite Te atom chains with different VEC(Te) in Tl₂Te₃ (left), LiTe₃ (center) and Te (right).

Figure 8

Infinite Te ribbons with different modifications in Cs₂Te₅ (top left), Rb₂Te₅ (top right) and In₂Te₅ (bottom center).

Figure 9

Different T nets in NbTe₄ (top left), CsTe₄ (top right) and Cs₃Te₂₂ (bottom center).

Figure 10

Planar layers of linear chains in U₂Te₅ (left), ZrTe₃ (center) and ZrSe₃ (right).

Figure 11

Layers of oligomeric Te atom fragments in Cs₂Te₂ (top left), ALnTe₄ (top right), RbTe₆ (bottom left), and CrTe₃ (bottom right).

Figure 12

Three-dimensional network of Te atoms in Cs₄Te₂₈.