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The Pb–Ag–Sb sulfide roshchinite, Cu0.09Ag1.04Pb0.65Sb2.82As0.37S6.08, is a lillianite homologue N=4 with a complex incommensurate superstructure in the 8.46 Å direction of the orthorhombic crystal lattice with a19.0804(1) Å, b8.4591(2) Å and c12.9451(3) Å, superspace group Pbcn(0σ20)00s, q=0.41458(3)b*. A structure solution and refinement in (3+1) superspace, based on 10,019 observed reflections and 437 refined parameters was terminated at Robs(wR) equal to 7.27 (8.07)% using satellites up to second order; Robsis 4.82 for main reflections only. The Pb atoms in trigonal coordination prisms on planes of unit-cell twinning are semiperiodically replaced by antimony. The marginal columns of (311)PbSslabs of the Sb–Ag based structure which is based on PbS-like topology contain Sb, Ag(Cu) and mixed Ag/Sb sites in a complicated sequence. Central portions of the slabs are occupied by Sb–S crankshaft chains, best exposed on the (100)PbSplanes, which run diagonally across the slabs. In these planes, in their majority the chains display Sb3S4form and two opposing orientations, zig-zagging along the [010] direction. Every six chains, a parallel configuration of two chains occurs, but occasionally this interval is reduced to five chains. This, together with related compositional changes in the Pb– and Ag–Sb column, explains the one-dimensionally incommensurate character of roshchinite. Modestly elevated contents of As replacing Sb are the probable reason of modulation and non-commensurability in roshchinite.

Cu1.78Bi4.73Se8, synthesized in a dry phase system Cu—Bi—Se at 450 °C, is monoclinic, a= 13.759 Å, b= 4.168 Å, c= 14.683 Å, γ= 115.61°, space group C2/m. It is an N = 3 member of the pavonite homologous series, with the composition limits Cu1.96Bi4.67Se8—Cu1.77Bi4.60S8—Cu1.25Bi4.91Se8. The crystal structure is composed of two types of alternating slabs, with configurations typical for the above series. The first kind of slabs contains paired square pyramidal columns of Bi3, interconnected by octahedral columns with three distinct statistical copper sites (flattened tetrahedral sites in the octahedral interior and a tetrahedral site between adjacent octahedra). They add up to nearly 1.5 Cu. The second kind of slabs contains central octahedra of Bi1, flanked by marginal distorted octahedra of Bi2. These Bi sites are partly replaced by statistically occupied Cu1-3 sites, in flat-tetrahedral and irregular trigonal-planar coordinations. Details of the Cu-for-Bi substitutions are discussed and comparisons with other N = 3 homologues of pavonite are made in the paper.

The crystal structure of Cu4Bi4Se9, synthesized at 400 °C, was determined from single crystal X-ray diffraction data and refined to the R1value of 0.05. The compound is orthorhombic, with a= 32.692 Å, b= 4.120 Å, and c= 12.202 Å, space group Pnma. The structure contains three square pyramidal Bi sites, an octahedrally coordinated Bi site as well as two tetrahedrally and two irregularly coordinated Cu sites. The structure is an intergrowth of PbS-like slabs with irregularly configured slabs of Bi pyramids and Cu tetrahedra. It contains covalently bonded Se2groups. Isotypy with Cu4Bi4S9is connected with substantial changes in coordination details for two out of five distinct Cu sites. Modular relationships to the structures of the cuprobismutite series of Cu—Bi sulfosalts can be expressed as different ways of recombination of the same large structural fragment in the structures of Cu4Bi4Se9and of the first cuprobismutite homologue, Cu4Bi5S10.

The crystal structure of synthetic Rb2Sb8S12(S2) · 2 H2O was determined from single crystal X-ray diffraction data: space group P21/n, Z= 2, a= 7.0750(17) Å, b= 25.403(8) Å, c= 8.0527(19) Å, β= 97.842(10)° (R1= 4.88% for 1050 reflections with Fo> 4σ[Fo]). The structure is composed of slabs with formal composition [Sb8S12] that are based on (110)PbScut-outs of the PbS archetype, are interspaced by channels with Rb+and H2O, and separated by S22-disulfide groups which also interconnect the slabs. Rb2Sb8S12(S2) · 2 H2O is a N1,2= 1,2 member of the hutchinsonite family of merotypes.

The crystal structure of Cu2.31TeS0.32, a sulfur-poor member of the solid solution series Cu61.3Te18.3S20.5- Cu61.9Te35.7S2.36prepared at 675°C, was determined and refined from single-crystal diffractometer X-ray data (R = 0.044). The quenched statistical cubic structure (a = 14.836(4)Å, space group F4132) consists at room temperature of two interpenetrating tetrahedral frameworks of icosahedral tellurium cages which enclose icosahedral clusters of half-occupied Cu positions centred by additional, fully occupied central copper sites. In one subset, statistically occupied sulfur tetrahedra occur in the tellurium cages, centred on this central Cu site.