Homologous Silver Bismuth Chalcogenide Halides (N, x)P. II. The (2, x)P and (3, x)P Structure Families of Modular Compounds with Tunable Composition and Structure

Abstract

AbstractThe crystal structures of two members of the solid solution series Ag3xBi5−3xS8−6xCl6x−1 (x = 0.52 (I), x = 0.67 (II)) and three compounds of the Ag4xBi6−4xQ10−8xBr8x−2 series (Q = S: x = 0.70 (III), x = 0.84 (IV); Q = Se: x = 0.72 (V)) were determined by single‐crystal X‐ray diffraction. The compounds crystallize in the monoclinic space group C2/m (No. 12) with a = 1326.7(3), b = 403.9(1), c = 1176.7(2) pm, β = 107.83(3)° for (I); a = 1325.4(3), b = 403.3(1), c = 1170.6(2) pm, β = 108.14(3)° for (II); a = 1338.9(4), b = 407.7(1), c = 1426.4(4) pm, β = 113.95(2)° for (III); a = 1346.7(4), b = 409.3(1), c = 1440.7(4) pm, β = 114.40(1)° for (IV); and a = 1370.9(2), b = 417.64(4), c = 1480.4(2) pm, β = 114.92(2)° for (V). (I) and (II) adopt the PbBi4S7 structure type, (III) to (V) crystallize in the CuBi5S8 type. All five compounds belong to the homologous series with general formula [BiQX]2[AgxBi1−xQ2−2xX2x−1]N+1 (Q = S, Se; X = Cl, Br; 1/2 ≤ x ≤ 1)), which resemble minerals of the pavonite series. They are characterized by the parameters N and x and are denoted (N, x)P. In the crystal structures, two kinds of layered modules alternate along [001]. Modules of type A uniformly consist of paired rods of face‐sharing 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 chains of edge‐sharing [MZ6] octahedra (M = Ag/Bi; Z = Q/X). These NaCl‐type fragments are of thickness N = 2 in Ag3xBi5−3xS8−6xCl6x−1 and N = 3 in Ag4xBi6−4xQ10−8xBr8x−2. All structures exhibit Ag/Bi disorder in octahedrally coordinated metal positions and Q/X mixed occupation of some anion positions.