Band 235, Heft 6-7

High temperature crystal structure of UPt 2 Si 2 determined using single-crystal neutron diffraction at 400 K is reported. It is found that the crystal structure remains of the primitive tetragonal CaBe 2 Ge 2 type with the space group P 4/ nmm . Anisotropic displacement factors of the Pt atoms at the 2 a (3/4 1/4 0) and Si atoms at the 2 c (1/4 1/4 z ) Wyckoff sites are found to be anomalously large.

In the frame of the studies on the phase relations in the ternary system Li–Sb–Sn at 300 °C the new ternary phase Li 8 Sb x Sn 3-x (0.3 ≤ x ≤ 1.0) was synthesized and characterized predominantly by single crystal and powder X-ray diffraction. The title compound crystallizes trigonally in the space group R 3‾$‾{3}$ m (no. 166), the lattice parameters are a  = 4.6962(11) Å and c  = 31.536(6) Å. The crystal structure of Li 8 Sb x Sn 3-x is described in the present paper. In addition, the stereochemical and topological relations to the phases with similar composition, namely Li 13 Sn 5 , Li 5 Sn 2 as well as cubic Li 3 Sb, besides native Li are discussed.

Based on the importance of the shock recovery experiments, the authors report the structural and optical properties of pure and 0.001 M dye-doped potassium dihydrogen phosphate (KDP) crystals for virgin and shock wave loaded samples. Rhodamine B and Methylene blue dyes are selected as dopants to be doped with KDP crystal for the present investigation. The test crystals of pure and doped KDP crystals are grown by slow evaporation technique and cut and polished crystals of (200) face are used for the present investigation. Table-top pressure driven shock tube is utilized for the shock wave generation and the used functional Mach number is 1.7. Virgin and shock wave loaded test crystals’ surface morphology, structural properties and optical transmissions are observed using optical microscope, powder X-ray diffractometer and UV-Visible spectrometer, respectively. Crystalline nature and optical transmission of pure and doped KDP crystals are found to have reduced by the impact of shock waves. It occurs due to the enhancement of defect concentration on the surface of the test crystals. From the observed results, we assert that the pure KDP crystal is relatively more stable to shock wave induced damage compared to doped KDP crystals as reflected by structural and optical studies.

One of the key parts of the crystal structure solution process from powder diffraction data is the determination of the lattice parameters from experimental data shortly called indexing. The successive dichotomy method is one of the most common ones for this process because it allows an exhaustive search. In this paper, we discuss several improvements for this indexing method that significantly reduces the search space and decrease the solution time. We also propose a combination of this method with other indexing methods: grid search and TREOR. The effectiveness and time-consumption of such algorithm were tested on several datasets, including orthorhombic, monoclinic, and triclinic examples. Finally, we discuss the impacts of the proposed improvements.

The temperature-dependent structure-property relationships of the aluminosilicate perrhenate sodalite |Na 8 (ReO 4 ) 2 |[AlSiO 4 ] 6 (ReO 4 -SOD) were analysed via powder X-ray diffraction (PXRD), Raman spectroscopy and heat capacity measurements. ReO 4 -SOD shows two phase transitions in the investigated temperature range (13 K <  T  < 1480 K). The first one at 218.6(1) K is correlated to the transition of dynamically ordered P4¯3n$P\overline{4}3n$ (> 218.6(1 K) to a statically disordered (<218.6(1) K) SOD template in P4¯3n$P\overline{4}3n$. The loss of the dynamics of the template anion during cooling causes an increase of disorder, indicated by an unusual intensity decrease of the 011-reflection and an increase of the Re-O 2 bond length with decreasing temperature. Additionally, Raman spectroscopy shows a distortion of the ReO 4 anion. Upon heating the thermal expansion of the sodalite cage originated in the tilt-mechanism causes the second phase transition at 442(1) K resulting in a symmetry-increase from P4¯3n$P\overline{4}3n$ to Pm3¯n$Pm\overline{3}n$, the structure with the sodalites full framework expansion. Noteworthy is the high decomposition temperature of 1320(10) K.

The solid-state structures of three H-bonded enol forms of 5-substituted 9-hydroxyphenalenones were investigated to accurately determine the H atom positions of the intramolecular hydrogen bond. For this purpose, single-crystal X-ray diffraction (SC-XRD) data were evaluated by invariom-model refinement. In addition, QM/MM computations of central molecules in their crystal environment show that results of an earlier standard independent atom model refinement, which pointed to the presence of a resonance-assisted hydrogen bond in unsubstituted 9-hydroxyphenalone, are misleading: in all our three and the earlier solid-state structures the lowest energy form is that of an asymmetric hydrogen bond (C S form). Apparent differences of results from SC-XRD and other analytical methods are explained.

In this study, a new air and moisture stable mononuclear cobalt(II)–carboxamide complex, [Co(TCrbx) 2 (CH 3 OH) 2 ](ClO 4 ) 2 , was synthesized and characterized (TCrbx = N -(4-methylpyridin-2-yl)thiophene-2-carboxamide). Complex characterization mainly was done with single crystal X-ray analysis. Ligand characterization was done with several spectroscopic techniques (Elemental Analysis, FT-IR, 1 H NMR, 13 C NMR). Cobalt(II) complex possesses distorted octahedral geometry coordinated with two carboxamide ligands at equatorial and two methanol ligands at axial positions and two perchlorate anions as counter ions. Synthesized complex was successfully tested as homogenous catalyst for the oxidation of benzyl alcohol with environmental friendly oxidant hydrogen peroxide (H 2 O 2 ) under mild conditions. Benzaldehyde was selectively obtained with the conversion value of 99.5% in dimethyl formamide after 3-h reaction time at 50 °C with 133 TON value. Solvent and temperature effects were also investigated.