Volume 235, Issue 1-2

The Na + solid state electrolyte Na 3 PS 4 is currently being investigated due to its high ionic conductivity and its synthesis-dependent crystal structure. Na 3 PS 4 adopts a tetragonal low-temperature modification with space group P  4̅2 1 c that transforms to a cubic high-temperature modification with space group I  4̅3 m (Tl 3 VS 4 type). These two modifications are related by a group-subgroup scheme. The symmetry reduction proceeds via a translationengleiche transition from I  4̅3 m to I  4̅2 m and subsequently via a klassengleiche transition to P  4̅2 1 c . The tetragonal phase with space group I  4̅2 m corresponds to the K 2 HgSnSe 4 type. The group-subgroup scheme of this tetragonal branch of the Bärnighausen tree is discussed along with the crystal chemical consequences and results of diffraction experiments. The structure of K 3 SbSe 4 (space group R  3 c ) belongs to the rhombohedral branch of the aristotype Tl 3 VS 4 .

Systematically twinned olivenite (Cu 2 (AsO 4 )OH) single crystals from Cap Garonne, Mine du Pradet, France, were studied by X-ray diffraction: P  2 1 / 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.

It is demonstrated by a detailed structural analysis that the crystallinity and the efficiency of small molecule based organic photovoltaics can be tuned by solvent vapor annealing (SVA). Blends made of the small molecule donor 2,2′-[(3,3′″,3″″,4′-tetraoctyl[2,2′:5′,2″:5″,2′″:5′″,2″″-quinquethiophene]-5,5″″-diyl)bis[(Z)-methylidyne(3-ethyl-4-oxo-5,2-thiazolidinediylidene)]]bis-propanedinitrile (DRCN5T) and the acceptor [6,6]-phenyl C71 butyric acid methyl ester (PC 71 BM) were annealed using solvent vapors with either a high solubility for the donor (tetrahydrofuran), the acceptor (carbon disulfide) or both (chloroform). The samples were analyzed by grazing-incidence wide-angle X-ray scattering (GIWAXS), electron diffraction, X-ray pole figures, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). A phase separation of DRCN5T and PC 71 BM is induced by SVA leading to a crystallization of DRCN5T and the formation of a DRCN5T enriched layer. The DRCN5T crystallites possess the two dimensional oblique crystal system with the lattice parameters a  = 19.2 Å, c  = 27.1 Å, and β  = 111.1° for the chloroform case. No major differences in the crystal structure for the other solvent vapors were observed. However, the solvent choice strongly influences the size of the DRCN5T enriched layer. Missing periodicity in the [010]-direction leads to the extinction of all Bragg reflections with k  ≠ 0. The annealed samples are randomly orientated with respect to the normal of the substrate (fiber texture).

Isomorphic symmetry reductions are a special class of klassengleiche symmetry reductions where the subgroup has the same space group type. The present contribution highlights five different isomorphic transitions of index 5 ( i 5), all from I  4/ m to I  4/ m . These superstructure formations allow (i) atom ordering in MoNi 4 , (ii) vacancy ordering in Nb 4 N 5 , K x Fe 2−y Se 2 and Nd 10 Au 3 As 8 O 10 and (iii) charge ordering in CsInCl 3 (≡Cs 2 In I In III Cl 6 ). The group-subgroup schemes in the Bärnighausen formalism are discussed along with the crystal chemical consequences.

Polycrystalline samples of LaRh 2 Ga 2 with the centrosymmetric CaBe 2 Ge 2 type structure were obtained by arc-melting. Small single crystals were grown through a special annealing sequence in an induction furnace. The structures of two different crystals were refined from diffractometer data, confirming the centrosymmetric structure. The 2 c Rh sites were refined with anharmonic atomic displacement parameters.

N-(N-benzoyl glycinyl)-N,N′-dicyclohexylurea was synthesised by conjugating N-benzoyl glycine and dicyclohexylcarbodiimide (DCC) using triethylamine as base catalyst. A single crystal X-ray diffraction study reveals that the compound self-assembles into a supramolecular sheet structure by intermolecular N–H · · · O, C–H · · · O hydrogen bonding and non-bonding van der Waals interactions. A high resolution transmission electronic microscopic (HR-TEM) image of the compound exhibits formation of fibrils in the solid state.