Homologous silver bismuth chalcogenide halides (N, x)P. III. The P(4,Px), P(5,P x), and P(7,P x) structure families of modular compounds with tunable composition and structure

Pierre Ferdinand P. Poudeu
Michael Ruck and Pierre F Poudeu Poudeu (2008)
Zeitschrift Fur Anorganische Und Allgemeine Chemie, 634(3):482490.
The crystal structures of six members of the homologous series with general formula [BiQX](2)[Ag(x)Bi(1x)Q(22x)X(2x)1](N+1) (Q = S, Se; X = Cl, Br; 1/2 <= x <= 1) and N = 4 5, or 7 were determined by singlecrystal Xray diffraction. The series are characterized by the parameters N and x and are denoted P(N,P x). Ag3Bi4S6Cl3 (X = 0.60) (I), Ag3.5Bi3.5S5Br4 (x = 0.70) (II) and Ag3.65Bi3.35Se4.70Br4.30 (x = 0.73) (III) belong to P(4,P x) series Ag5x Bi(75x)Q(1210)x X 10(x3) and adopt the AgBi6S9 structure type. The P(5,P x) compound Ag3.66Bi4.34S6.68Br3.32 (IV), which corresponds to x = 0.61 in Ag6xBi86xS1412x Br12x4, crystallizes isostructurally to AgBi3S5 center dot The compounds Ag4.56Bi5.44Se8.88Br3.12 (x = 0.57) (V) and Ag5.14Bi4.86S7.76Br4.24 (x = 0.64) (VI), which are members of P(7,P x) series Ag(8x)Bi(108x)Q(1816x)Br(16x6), adopt the Ag3Bi7S12 structure type. In the monoclinic crystal structures (space group C2/m) two kinds of layered modules alternate along [001]. Modules of type A uniformly consist of paired rods of facesharing monocapped trigonal prisms around Bi atoms with octahedra around mixed occupied metal positions (M Ag/Bi) between them. Modules of type B are composed of [MZ(6)] octahedra, which are arranged in NaCltype fragments of thickness N. All structures exhibit Ag/Bi disorder in octahedrally coordinated metal positions as well as Q/X mixed occupation of some anion positions. Corresponding to their black color, all compounds are narrowgap semiconductors (Eg = 0.35 eV for (II)). General characteristics of the entire class of P(N x) compounds are gathered in a catalogue.
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