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BaSO4, orthorhombic, Pnma (no. 62), a = 8.8806(8) Å, b = 5.4539(5) Å, c = 7.1570(7) Å, V = 346.64(6) Å3, Z = 4, Rgt (F 2) = 0.0141, wRref (F 2) = 0.0329, T = 293 K.

The metal-rich phosphide TaCrP forms from the elements by step-wise solid state reaction in an alumina crucible (maximum annealing temperature 1180 K). TaCrP is trimorphic. The structural data of the hexagonal ZrNiAl high-temperature phase (space group P 6 ‾ 2 m $P\overline{6}2m$ ) was deduced from a Rietveld refinement. At room temperature TaCrP crystallizes with the TiNiSi type (Pnma, a = 623.86(5), b = 349.12(3), c = 736.78(6) pm, wR = 0.0419, 401 F 2 values, 20 variables) and shows a Peierls type transition below ca. 280 K to the monoclinic low-temperature modification (P121/c1, a = 630.09(3), b = 740.3(4), c = 928.94(4) pm, β = 132.589(5)°, wR = 0.0580, 1378 F 2 values, 57 variables). The latter phase transition is driven by pairwise Cr–Cr bond formation out of an equidistant chain in o-TaCrP. The phase transition was monitored via different analytical tools: differential scanning calorimetry, powder synchrotron X-ray diffraction, magnetic susceptibility measurements and 31P solid state NMR spectroscopy.

The equiatomic metal-rich phosphide NbCrP shows a structural phase transition around 125 K. The structures of the high- and low-temperature modifications were refined from single crystal X-ray diffractometer data of an un-twinned crystal: TiNiSi type, Pnma, a = 619.80(2), b = 353.74(4), c = 735.24(6) pm, wR = 0.0706, 288 F 2 values, 20 variables at 240 K and P121/c1, a = 630.59(3), b = 739.64(4), c = 933.09(5) pm, β = 132.491(6)°, wR = 0.0531, 1007 F 2 values, 57 variables at 90 K. The structural phase transition is of a classical Peierls type. The equidistant chromium chain in HT-NbCrP (353.7 pm Cr–Cr) splits pairwise into shorter (315.2 pm) and longer (373.2 pm) Cr–Cr distances. This goes along with a strengthening of Cr–P bonding. The superstructure formation is discussed on the basis of a group–subgroup scheme. Electronic structure calculations show a lifting of band degeneracy. Protection of the non-symmorphic symmetry of space group Pnma is crucial for the phase transition. The estimated charge modulation is consistent with the interpretation as Peierls transition.

Linarite, PbCuSO4(OH)2, crystallizes as secondary mineral in form of clusters of crystals in Mine du Pradet at Cap Garonne in France. A tiny single crystal was isolated and its structure was refined from synchrotron diffraction data (λ = 0.049592 nm): P121/m1, a = 467.75(2), b = 563.48(4), c = 967.64(5) pm, β = 102.647(5)°, wR = 0.0544, 819 F 2 values and 56 variables. The proton positions were also refined. The Cu2+ cations are located within Cu(OH)2 ribbons and exhibit pronounced Jahn-Teller distortion (d(Cu–O): 2 × 191.9, 2 × 197.3 and 2 × 252.8 pm). The Cu(OH)2 ribbons are condensed with the sulfate tetrahedra and the lead cations. The latter are coordinated to eight oxygen atoms in a slightly anisotropic manner. Calculations of the electron localization function (ELF) of PbO (litharge), PbSO4 (anglesite) and PbCuSO4(OH)2 (linarite) show pronounced lone-pair character for PbO but rather isotropic ELF values around the lead cations in PbSO4 and PbCuSO4(OH)2.

Systematically twinned olivenite (Cu2(AsO4)OH) single crystals from Cap Garonne, Mine du Pradet, France, were studied by X-ray diffraction: P 21/n, a = 822.69(6) pm, b = 861.88(9) pm, c = 594.06(9) pm, β = 90.000(6)°, wR = 0.0224, 1621 F 2 values, 79 variables and a domain ratio of 0.501(1)/0.499(1). The temperature dependence of the magnetic susceptibility was well reproduced with a square-spin cluster model and an antiferromagnetic spin-exchange parameter of J/k B = 157(3) K.

The gold-rich intermetallic compounds REAu4Cd2 (RE = La–Nd, Sm) were synthesized from the elements in sealed tantalum ampoules. Their characterization by X-ray powder and single crystal data confirmed the tetragonal YbAl4Mo2 type, space group I4/mmm. The basic building units are Au4 squares (278 pm Au–Au in CeAu4Cd2) and infinite linear cadmium chains (275 pm Cd–Cd in CeAu4Cd2). We exemplarily studied the solid solution CeAu4+ x Cd2− x for x = 0–1 up to CeAu5Cd. Electron diffraction patterns on a CeAu5Cd sample confirm the single crystal data. They give no hint for complete gold-cadmium ordering. Temperature-dependent magnetic susceptibility measurements of CeAu4Cd2, CeAu5Cd, PrAu4Cd2 and NdAu4Cd2 show stable trivalent rare earth ions and give no hint for magnetic ordering above 3 K.

Natural lead dioxide samples (β modification) from Cap Garonne, Mine du Pradet, France and Mount Trevasco, Italy were studied by single crystal X-ray and electron diffraction, clearly manifesting the rutile-type structure. A needle from the Mount Trevasco sample was investigated on a single crystal diffractometer: P42/mnm, a = 495.81(10), c = 338.66(7) pm, wR = 0.0513, 117 F 2 values (all data) and nine variables (293 K data). An additional data set at T = 90 K gave no hint for structural distortions.

The liquid CO2-extract of aged burley tobacco was investigated for its content of diterpenoids, which are considered as important precursors of flavour constituents. Among several cembranoids, already known from various tobacco types, 4,8-dimethyl-8-hydroxy-11-(1-methyl-ethyl)-14-oxo-pentadeca-5,9-diene-4-olide, a new natural product, could be identified, evidently originating from 2,6,11-cembratriene-4,8-diol by oxidative cleavage of the 11,12-double bond with subsequent cyclization to the seco-lactone 14.