Volume 236, Issue 11-12

Pb 2 Sc 2 Si 2 O 9 and Pb 2 In 2 Si 2 O 9 , respectively, the scandium and indium containing structural analogues of the mineral kentrolite are grown by spontaneous crystallization from a PbO flux. The corresponding polycrystalline powder samples are synthesized by conventional solid-state approach. The compounds are thoroughly characterized using temperature-dependent single crystal and powder X-ray diffraction, heat capacity measurements, second harmonic generation experiments and Raman spectroscopy. At ambient conditions, both compounds crystallize in the non-centrosymmetric Pna 2 1 space group and undergo phase transitions to the centrosymmetric Pbcn space group at elevated temperatures. The Pbcn into Pna 2 1 phase transitions are complemented by the signals of the temperature-dependent second harmonic generation. The specific heat capacity exhibits distinct cusp, supporting the λ -type second-order phase transition. The temperature dependency of some selective Raman modes further complements the findings, showing softening and hardening of the phonons across the phase transitions.

The ternary platinides CaGa 5 Pt 3 ( a  = 2082.5(4), b  = 406.05(8), c  = 739.2(1) pm) and EuGa 5 Pt 3 ( a  = 2085.5(5), b  = 412.75(9), c  = 738.7(1) pm) were synthesized from the elements in sealed high-melting metal tubes in an induction furnace. CaGa 5 Pt 3 and EuGa 5 Pt 3 are isotypic with CeAl 5 Pt 3 and isopointal with the YNi 5 Si 3 type intermetallic phases (space group Pnma , oP 36 and Wyckoff sequence c 9 ). The structure of EuGa 5 Pt 3 was refined from single crystal X-ray diffractometer data: w R 2 = 0.0443, 1063 F 2 values and 56 variables. The gallium and platinum atoms build up a three-dimensional [Ga 5 Pt 3 ] 2− polyanionic network in which the europium atoms fill slightly distorted hexagonal prismatic voids. The Ga–Pt distances within the network range from 249 to 271 pm, emphasizing the covalent bonding character. Temperature dependent magnetic susceptibility measurements indicate diamagnetism for CaGa 5 Pt 3 and isotypic BaGa 5 Pt 3 . EuGa 5 Pt 3 behaves like a Curie–Weiss paramagnet above 50 K with an experimental magnetic moment of 8.17(1) µ B /Eu atom, indicating divalent europium. Antiferromagnetic ordering sets in at T N  = 8.5(1) K. The divalent ground state of europium is confirmed by 151 Eu Mössbauer spectroscopy. EuGa 5 Pt 3 shows a single signal at 78 K with an isomer shift of −9.89(4) mm s −1 . Full magnetic hyperfine splitting with a hyperfine field of 25.0(2) T is observed at 6 K in the magnetically ordered regime.

Phosphoric triamides are attractive to investigate because of their extensive applications in various fields, especially in medicine. Five new phosphoric triamides with the main parts [N]P(O)[NH] 2 and [C(O)NH]P(O)[N] 2 have been structurally analyzed by single crystal MoKα/synchrotron-based X-ray diffraction and characterized by spectroscopic methods (FT-IR and 1 H, 13 C, 31 P NMR). Compounds crystallize in orthorhombic ( 1 with space group Pnma ) and monoclinic ( 2 ( P 2 1 / a ), 3 ( C 2/ c ), 4 ( P 2 1 / n ) and 5 ( P 2 1 / c )) crystal systems. The asymmetric unit of all structures consists of one phosphoric triamide molecule, except for 1 with one half of molecule. X-ray crystallography data reveal that the molecular architectures constructed by classical N—H … O hydrogen bonds are as 1D linear (building the R 2 1 ( 6 ) ${R}_{2}^{1}\left(6\right)$ , C (4) and R 2 2 ( 10 ) / R 2 1 ( 6 ) ${R}_{2}^{2}\left(10\right)/{R}_{2}^{1}\left(6\right)$ motifs, respectively, for 1 – 3 ) or dimeric (the R 2 2 ( 8 ) ${R}_{2}^{2}\left(8\right)$ ring motif for 4 and 5 ). A detailed investigation of the intermolecular interactions using Hirshfeld surface (HS) analysis illustrates that the H … H, O … H/H … O and C … H/H … C contacts for all compounds, and Cl … H/H … Cl and F … H/H … F contacts for 3 – 5 , are the most significant contributors to the crystal packing. Moreover, based on the calculated enrichment ratios ( E ), the O … H/H … O contacts including the classical N—H … O hydrogen bonds for all structures are considered as favoured contacts.

The crystal structure of Sc 3 Ir 4 Si 13+ x ( x  = 0.22) [space group P m 3 ‾ n $Pm\bar{3}n$ , a  = 8.4651(1) Å] is found to be a new disordered variant of the primitive cubic Yb 3 Rh 4 Sn 13 Remeika prototype. The silicide is stable in the narrow temperature range of 1283–1397 °C and reveals metallic properties. The crystal structure of Sc 4 Ir 7 Ge 6 [U 4 Re 7 Si 6 type, space group I m 3 ‾ m $Im\bar{3}m$ , a  = 8.1397(8) Å] is refined for the first time. The electronic band structure calculations reveal that the properties of this germanide can be explained based on the free electron gas model. Both compounds reveal close structural relationships to the simple perovskite structure.

Diffraction techniques are well-established methods for crystal structure determination as well as phase identification and quantification. Raman spectroscopy can be a valuable complementary characterization technique, because in contrast to the former it yields also information on amorphous materials and it is a probe for short-range structural effects. The herein presented setup allows for simultaneous neutron diffraction and Raman spectroscopy, shown with a sample of lead sulfate under ambient conditions as a proof of principle. In order to fulfil requirements of both methods, a sapphire single-crystal is used as a sample holder. Practical considerations for successful simultaneous in situ neutron diffraction and Raman spectroscopic measurements are given.