Six New Members of the A₂M^IIM^IV₃Q₈ Family and Their Structural Relationship

Abstract

The A 2 M II M IV 3 Q 8 family (A = alkali metal; M II = divalent metal; M IV = tetravalent metal; Q = chalcogenide) has attracted much attention because of its diverse structures and properties. Herein, we have successfully synthesized six new compounds as the first Mn-containing members of this family, Cs

Centrosymmetric or Noncentrosymmetric? Transition Metals Talking in K2TGe3S8(T = Co, Fe)

“…4) space group as confirmed by the second harmonic generation (SHG) response. K 2 FeGe 3 S 8 belongs to the well-known A 2 M II M Iv 3 Q 8 (A = alkali metals, M II =divalent transition metals, M IV = Ge or Sn, Q = S or Se) system, which mainly features a layered crystal structure. − K 2 CoGe 3 S 8 forms in a new structure type with a centrosymmetric P (no. 2) space group.…”

Intriguing Dimensional Transition Inducing Variable Birefringence in K2Na2Sn3S8 and Rb3NaSn3Se8

“…In the structure, the S–Sn–S angles in the Sn(1)­S 5 trigonal bipyramids range from 84.93(7)° to 171.10(7)°, and from 94.52(10)° to 119.09(11)° for Sn(2)­S 4 tetrahedra. These bond lengths and angles are matched well with those in the other reported compounds. , The bond valence calculations resulted in values of 1.14 for the Na + cation, 1.09 for the K + cation, 3.97–3.98 for the Sn 4+ cations, and 1.95–2.12 for the S 2– anions (Table S2).…”

Triclinic Layered A2ZnSi3S8 (A = Rb and Cs) with Large Optical Anisotropy and Systematic Research on the Inherent Structure–Performance Relationship in the A2MIIBMIV3Q8 Family

“…Surveying the crystal structures in the 2–1–3–8 A 2 M II M IV 3 Q 8 system, − they crystallize in the five different space groups: triclinic P 1̅, monoclinic ( P 2 1 and P 2 1 / n ), orthorhombic P 2 1 2 1 2 1 , and cubic Pa 3̅. Among these, Zn and Sn atoms are occupied in one site with Zn/Sn = 0.25:0.75 in the structure of high-symmetry β-K 2 ZnSn 3 S 8 (cubic Pa 3̅), which is different with the fully occupied sites of Group 12 and Group 14 atoms in low-symmetrical compounds (from orthorhombic to triclinic) (Figure ).…”

“…Therefore, monoclinic and orthorhombic compounds exhibit similar torsion resistances of layers that are still much smaller than those in the triclinic compounds. The previously proposed structure mismatch factor F is only suitable for the change rule of structural types on the monoclinic and orthorhombic compounds, and this factor cannot be considered in the triclinic A 2 ZnSi 3 S 8 (A = Rb and Cs). In view of their layered structures, they have the chance to possess a large optical anisotropy as potential birefringent materials.…”

“…Inorganic functional materials have been attracted many attentions in various application fields because of their multiple crystal structures and flexible physicochemical properties. − As for chalcogenides, survey on their structures shows that they have the different dimensionalities from zero-dimensional (0D) to 3D network through the chemical substitution, and many systems have been discovered so far, for example, A-M II 4 -M IIIA 5 -Q 12 (A = K, Rb, and Cs; II = Zn, Cd, Hg, and Mn; IIIA = Ga, and In; Q = chalcogen) compounds have shown superior second harmonic generation (SHG) responses, fluorescence emission, and magnetic properties as potential multifunctional materials. − Other famous research systems include the diamondlike semiconductors I 2 -II-IV-Q 4 (DLSs), , AE-I 2 -IV-Q 4 (AE = Sr and Ba; I = Li, Ag, Cu, and Na; IV = Si, Ge, and Sn; Q = chalcogen), − and the RE 3 -M-M′-Q 7 P6 3 family, − and so on. Another important family is the A 2 M II M IV 3 Q 8 family (2–1–3–8 system: A = monovalent alkali metal; M II = divalent transition metals; M IV = group 14 metals; Q = chalcogen). − In the above 2–1–3–8 system, many compounds were discovered and they crystallize in the various space groups, such as P 1̅, P 2 1 , P 2 1 / n , P 2 1 2 1 2 1 and cubic Pa 3̅. For instance, K 2 ZnSn 3 S 8 compounds exhibit a phase-change behavior (α: P 1̅ vs β: Pa 3̅) that is also viewed as the only one discovered polymorph in this 2–1–3–8 system; K 2 FeGe 3 Se 8 and K 2 MnGe 3 S 8 show the potential magnetic performances with interesting antiferromagnetic transition at ∼10 and 8.1 K, respectively. , Besides, several of noncentrosymmetrical (NCS) P 2 1 compounds (K 2 ZnSn 3 Se 8 , K 2 ZnGe 3 S 8 , and K 2 MnGe 3 S 8 ) exhibit the considerable powder SHG responses based on experimental evaluation; − Cs 2 HgSn 3 Se 8 crystal possesses the strong photoconductivity effect ((μτ) h|| = 7.78 × 10 –5 cm 2 /V) .…”