Volume 234, Issue 9

In this research article, the authors pay attention to investigate the effect of structural and dielectric properties of ammonium dihydrogen phosphate (ADP) crystal under pre and post shock loaded conditions. A shock wave of Mach number 1.9 was utilized for the present investigation which was generated by a table-top pressure driven shock tube. The crystalline nature and grain size variations were estimated by powder X-ray diffraction technique. The grain size of post shock wave loaded ADP crystal is found to be larger than that of the pre shock wave loaded ADP crystal. The dielectric properties of the pre and post shock loaded crystals were analyzed by impedance analyzer as a function of frequency (1 kHz–1 MHz) at ambient temperature. The dielectric constant is observed to be varying from 346 to 362 at the frequency of 400 kHz for pre and post shock wave loaded ADP crystals, respectively. The obtained results suggest that shock waves can be an alternate tool to tailor the physical properties of materials without creating any change in the original crystal system and surface morphology.

A series of six new single crystals of fully stoichiometric As 3+ -bearing Mo-oxides and partially W-substituted Mo-oxides with formula As m O(Mo 1− x W x O 3 ) p ( m  = 1, 2; p  = 5, 7, 9, 10 and 11 and 0 ≤  x  ≤ 0.6) was successfully grown using vapor-phase transport in vacuo . The crystal structures were determined using single-crystal X-ray diffraction data. All these compounds exhibit acentric orthorhombic symmetry with Z  = 2, and belong to the so-called ( n )-ITB (intergrowth tungsten bronzes) family, with n  = 2, 3, 4 and 5. The six ( n )-ITB phases have the following formulae: (2)-AsMo 5 O 16 ( Pm  2 a ), (2)-As 2 Mo 10 O 31 ( Pma  2), (3)-AsMo 7 O 22 ( Pmn  2 1 ), (3)-As(Mo 5.53 W 1.47 )O 22 ( Pmn  2 1 ), (4)-As(Mo 4.33 W 4.67 )O 28 ( Pm  2 a ) and (5)-As(W 6.63 Mo 4.37 )O 34 ( Pmn  2 1 ). Their structures consist of vertex-sharing MO 6 octahedral units (with M either Mo or Mo/W) connected so as to form three-dimensional frameworks. Such frameworks consist of perovskite tungsten bronzes (PTB) type slabs, from 2- to 5-octahedra wide, intergrown with single hexagonal tungsten bronzes (HTB) type slabs, stacked up to form pseudo-hexagonal tunnels along the a -axis. As 3+ and additional oxygen atoms are located in off-center positions inside the tunnels, forming As–O bonds with peculiar arrangements. In particular, we obtained the first examples of structures where, besides the usual AsO 3 E distorted pyramidal geometry, As 3+ adopts AsO 4 E coordination with a seesaw configuration.

The new ternary compound La 3 Ni 4 Al 2 has been synthesized and the crystal structure has been studied by X-ray single crystal diffraction. La 3 Ni 4 Al 2 is the first aluminide, crystallizing in the La 3 Ni 4 Ga 2 -type. The crystal structure of La 3 Ni 4 Al 2 consists of La-layers and hetero-atomic Ni/Al layers, sequentially alternating along the a axis (pseudo-hexagonal c axis). According to electronic structure calculations using the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation (TB-LMTO-ASA), strong Al–Ni interactions have been established. The coordination polyhedra for the Al atoms are cuboctahedra, whereas the bicapped square prism and bicapped square antiprism are typical for nickel atoms. The lanthanum atoms are enclosed in pseudo Frank–Kasper polyhedra.

Radiation induced disorder in gadolinite that led to metamictization with an upper degree of amorphization of 18% was thermally annealed between room temperature and 1273 K. The degree of annealing was calibrated using the anti-symmetric Si–O–Si Raman-active stretching mode near 902 cm −1 . Annealing increased with increasing temperature with a rapid critical recrystallization at ca. 943 K. This annealing on a short length scale was then complemented by investigations of long-range ordering seen by X-ray diffraction. The same critical temperature was found, and in addition further increase of long-range order extended to 1073 K. Metamict gadolinite contains only Fe 2+ within experimental uncertainty.

In the current work we have studied the crystallographic relationship between the AT 2 Al 10 phases (where A = actinide, lanthanide and rare earth element and T = transition metal). It is known that with this stoichiometry two structure types exist: tetragonal CaCr 2 Al 10 and orthorhombic YbFe 2 Al 10 . It was found that both CaCr 2 Al 10 and YbFe 2 Al 10 types are structural derivatives of the ThMn 12 type structure (which has more general formula of AT x Al 12− x , with x  > 2). CaCr 2 Al 10 structure has a group-subgroup relationship with the ThMn 12 structure, while the relationship of the YbFe 2 Al 10 to the ThMn 12 was proved applying the strong reflection approach, suggested initially for approximants of quasi-crystals. Proposed here relationship between the studied structures explains the small difference in total energies, calculated using Density Functional Theory. Understanding the connection between these phases allows regarding AT 2 Al 10 composition as somewhat extension of the AT x Al 12− x compositional range. Due to the unique magnetic properties of the AT x Al 12− x phases, tunable as a function of crystallographic structure, study of structural stability and crystallographic relationships of related phases are of outmost importance.

Synthesis of C-2 N-substituted anthranilamide derivatives was carried out in a straight forward manner, utilizing 2-aminobenzamide and benzyl chloride as starting materials. Their crystal structures have been established by single crystal X-ray crystallographic method. In the molecules of 2-benzylamino-benzamide (3a) , intramolecular hydrogen bonding b/w O atom and proton of –NH and classical intermolecular hydrogen bonding of the type N–H · · · O forming eight membered rings in R 4 2 (8) pattern. In both molecules of 2-(dibenzylamino)benzamide (3b) , unlike the molecule in 3a , each H atoms is pointed towards N atom causing intramolecular hydrogen bonding interactions, resulting in S(6) motifs. However, it is interesting to note that both molecules in 3b are lying about inversion centres and form dimers in R 4 2 (8) motifs; the two dimers are linked via non-classical intermolecular hydrogen bonds C–H · · · O resulting in clusters of four molecules in the structure. In vitro assay results revealed that molecule 3b with IC 50 values of 3.8 ± 0.08 μM (AChE) and 17.6 ± 1.10 μM (BChE) possessed better cholinesterase (AChE and BChE) inhibition potential as compared to standard drug galantamine. Preliminary in silico studies showed that more biological active derivatives were also having good pharmacokinetic profile with no AMES toxicity and carcinogenicity.

The molecular and single crystal structure of O , O -diethyl O -[2-(dimethylamino)ethyl] phosphorothioate oxalate, as determined by single crystal X-ray diffraction studies, is described for the first time; although this compound is well-known by industry and research from the mid-20 th century. The known decomposition product of pure O , O -diethyl O -[2-(dimethylamino)ethyl] phosphorothioate could also be structurally characterized. Additionally, the compounds are characterized by recent analytical methods e.g. NMR. The findings of our study support the thesis that the isolated decomposition product must be a by-product of the thiono-thiolo rearrangement process of the title compound.