Space Groups

In (2RS,6SR)-N-diphenylacetyl-2,6-diphenylpiperidin-4-one, C 31 H 27 NO 2 , (I), the piperidinone ring adopts an almost ideal twist±boat conformation, and the molecules are linked into sheets by a combination of one CÐHÁ Á ÁO hydrogen bond and one CÐHÁ Á Á%(arene) hydrogen bond. (2RS,3SR,5RS,6SR)-3,5-Dimethyl-2,6-diphenyl-N-phenylacetylpiperidin-4-one, C 27 H 27 NO 2 , (II), crystallizes with Z H = 2 in the space group P1; the piperidinone rings adopt an almost ideal boat conformation in one of the molecules and a conformation between boat and twist±boat in the other. The molecules of (II) are linked into sheets by a combination of ®ve CÐHÁ Á ÁO hydrogen bonds and one CÐHÁ Á Á%(arene) hydrogen bond.

The structures of two Nb and two Mn-Nb (oxy)nitrides have been refined from Cu Ka powder diffractometer data by the Rietveld 1 method and have been characterised by electron diffraction. The phases Nb N O and Mn Nb N O have structures 3.49 4.56 0.44 0.54 3.07 4.40 0.60 related to that of Nb N , an NaCl type with ordered metal vacancies. Refinements in space group I4/m, with R 51.3% and 1.1%, 4 5 F respectively, have shown that they are disordered and that metal atoms partially occupy both the nominally filled 8h position and the nominally empty 2a position in the Nb N type. The observed bond lengths indicate that the 2a position is occupied only by Mn atoms in 4 5 Mn Nb N O . The Nb N type structure of Nb (N,O) and the related structure of MnNb (N,O) has been refined in space 0.54 3.07 4.40 0.60 5 6 5 6 2 3 group P6 /mcm to R 51.5% and 2.9%, respectively. In the latter, the trigonal prism sites 6g are found to be occupied only by Nb, the 3 F octahedral 4d sites by approximately equal amounts Mn and Nb and the octahedral 2a site, empty in the Nb N type structure, only by 5 6 Mn. The Nb (oxy)nitride structures exhibit short Nb-Nb distances which indicates localised bonding between Nb atoms. Magnetic susceptibility and electrical conductivity measurements of the tetragonal phases at 15-300 K show, respectively, small magnetic moments which are coupled in an antiferromagnetic manner at low temperatures and poor, nearly temperature-independent, conductivities.

The new concept, anion substitution, is explored for possible improvement of hydrogen storage properties in the system LiBH 4 -LiI. The structural chemistry and the substitution mechanism are analyzed using Rietveld refinement of in situ synchrotron radiation powder X-ray diffraction (SR-PXD) data, attenuated total reflectance infrared spectroscopy (ATR-IR), differential scanning calorimetry (DSC) and Sieverts measurements. Anion substitution is observed as formation of two solid solutions of Li(BH 4 ) 1-x I x , which merge into one upon heating. The solid solutions have hexagonal structures (space group P6 3 mc) similar to the structures of h-LiBH 4 and ␤-LiI. The solid solutions have iodide contents in the range ∼0-62 mol% and are stable from below room temperature to the melting point at 330 • C. Thus the stability of the solid solutions is higher as compared to that of the orthorhombic and hexagonal polymorphs of LiBH 4 and ␣and ␤-LiI. Furthermore, the rehydrogenation properties of the iodide substituted solid solution Li(BH 4 ) 1-x I x , measured by the Sieverts method, are improved as compared to those of LiBH 4 . After four cycles of hydrogen release and uptake the Li(BH 4 ) 1-x I x solid solution maintains 68% of the calculated hydrogen storage capacity in contrast to LiBH 4 , which maintains only 25% of the storage capacity after two cycles under identical conditions.

We have attempted to grow single crystals of Ce-Ni-Ge ternary system having layered structure. Several polycrystalline samples, CeNiGe x (2 < x < 3), Ce 3 Ni x Ge y (1.6 < x < 2, 6.5 < y < 8.5) and Ce 2 NiGe 6 , were prepared by an arc-melting of constituent elements. All samples grown by the Czochralsky method are found to contain the phase of the orthorhombic CeNiGe 2 type structure. A Rietveld method was applied to analyze the crystal structure of CeNiGe 2.2 using X-ray powder diffraction data at room temperature. The refined lattice parameters were a = 4.260 Å, b = 16.81 Å and c = 4.209 Å with the space group Cmmm. The temperature dependence of magnetic susceptibility shows a significant variation in the magnetic properties depending on the concentration of Ge, that is, magnetic phase transition temperature depends on starting materials. It may come from the fact that the magnetic property relies on a structural homogeneity and a stoichiometry.

Reagents and solvents used in the syntheses of 2 and 3 were purchased from commercial sources and used without further purification. Elemental analyses (C, H, N) were performed with an EA 1108 CHNS/0 automatic analyzer. A mixture of tris-methyl-1,3,5-benzenetricarboxylate (5 g, 0.02 mol) and the primary amine (10.0 ml), ethylamine (3.0 g, 0.066 mol) and propylamine (7.19 g, 0.121 mol) for 2 and 3, respectively, were stirred in 40 ml of DMF during 24 h at 100°C. Single colorless needle crystals of 2 and 3 were obtained from the recrystallization of the solid in a ethanol/H 2 O solution. Spectral data for 2. 1 H NMR: 8.67 (t, 3H), 8.35 (s, 3H), 3.33 (m, 2H), 1.16 (t, 3H). 13 C NMR: 165.8 (C=O), 135.4 (C arom -R), 128.

This graduate-level textbook deals with different aspects of plane mirrors and mirror-related symmetries. It provides us with some new ways of understanding symmetries in crystals and the mirror combination schemes. The inclusion of topics such as the Wigner–Seitz unit cell, reciprocal lattice, Brillouin zones, diffraction of crystals, etc., based on the mirror combination scheme, are extremely helpful in understanding many other concepts in crystallography. A mirror is the only fundamental symmetry in crystals, and all other permissible symmetries in crystalline solids can be derived from suitable combinations of mirrors, called derived symmetries. A rudimentary knowledge of symmetry in crystallography is essential to students, researchers, and professionals in many subjects in science and technology: physics, chemistry, mathematics, molecular biology, geology, metallurgy, and particularly materials science and mineralogy.

The fractions of aluminium, [Al]/[Al þ Si], and oxygen, [O]/[O þ N], in crystallographically distinct sites of BaYb[Si 4-x Al x O x N 7-x ] oxonitridoaluminosilicate (space group P6 3 mc, No. 186) were refined based on the results of neutron powder diffraction for a synthetic sample with the composition of x ¼ 2.2(2) and simulated as functions of temperature for the compositions x ¼ 2 and x ¼ 2.3 using a combination of static lattice energy calculations (SLEC) and Monte Carlo simulations. The SLEC calculations have been performed on a set of 800 structures differing in the distribution of Al/Si and O/N within the 2 Â 2 Â 2 supercell containing 36 formula units of BaYb[Si 4-x Al x O x N 7-x ]. The SLEC were based on a transferable set of empirical interatomic potentials developed within the present study. The static lattice energies of these structures have been expanded in the basis set of pair-wise ordering energies and on-site chemical potentials. The ordering energies and the chemical potentials have been used to calculate the configuration energies of the oxonitridoaluminosilicates (so-called sialons) using a Monte Carlo algorithm. The simulations suggest that Al and O are distributed unevenly over two non-equivalent T(Si/Al) and three L(N/O) sites, respectively, and the distribution shows strong dependence both on the temperature and the composition. Both simulated samples exhibit order/disorder transitions in the temperature range 500-1000 K to phases with partial long-range order below these temperatures. Above the transition temperatures the Si/Al and N/O distributions are affected by short-range ordering. The predicted site occupancies are in a qualitative agreement with the neutron diffraction results.

The fractions of aluminium, [Al]/[Al + Si], and oxygen, [O]/[O + N], in crystallographically distinct sites of BaYb[Si4–x Al x O x N7–x ] oxonitridoaluminosilicate (space group P63 mc, No. 186) were refined based on the results of neutron powder diffraction for a synthetic sample with the composition of x = 2.2(2) and simulated as functions of temperature for the compositions x = 2 and x = 2.3 using a combination of static lattice energy calculations (SLEC) and Monte Carlo simulations. The SLEC calcu lations have been performed on a set of 800 structures differing in the distribution of Al/Si and O/N within the 2 × 2 × 2 supercell containing 36 formula units of BaYb[Si4–x Al x O x N7–x ]. The SLEC were based on a transferable set of empirical interatomic potentials developed within the present study. The static lattice energies of these structures have been expanded in the basis set of pair-wise ordering energies and on-site chemical potentials. The ordering energies and the chemica...

Four compounds Co(SS-H 2 bzimed-H) 2 • CH 3 OH • 2H 2 O (1), Zn 4 (SS-H 2 bzimed-H) 4 (NO 3 ) 4 • 5H 2 O (2), Co 5 (Hbzimed-H) 6 Cl 4 • 2.5H 2 O (3), Ni 5 (Hbzimed-H) 6 Cl 4 have been synthesized by methods of alternative hydroponic and hydrothermal reactions, and their crystal structures were determined. Room temperature reaction of SS-H 2 bzimed with Co(NO 3 ) 2 • 6H 2 O yielded compound 1 which crystallizes in the chiral orthorhombic space group C222 1 , where SS-H 2 bzimed ligands act as facially tridentate ligands through both bis-benzimidazole nitrogen atoms and one deprotonated hydroxyl group. By using Zn(NO 3 ) 2 • 6H 2 O instead of Co(NO 3 ) 2 • 6H 2 O, under refluxed stirring at 80 °C, compound 2 was obtained similarly to 1 which crystallizes in the chiral monoclinic space group C2, showing a Zn 4 [µ 3 -O] 4 cubic core constructed by four monodeprotonated, µ 3 -κN,O:κO,O′:κN′,O′-SS-H 2 bzimed ligands. Under 140 °C at hydrothermal conditions, the SS-H 2 bzimed ligand unexpectedly changes to Hbzimed by an in situ intramolecular dehydration coupling reaction, and the neonatal ligands bridge metal systems into two kinds of rare single crystal microtubes constructed by a trigonal bipyramid M 5 [µ-O] 6 (M ) Co II : 3, Ni II : 4) core where each apical O h metal atom is linked to equatorial T d metal atoms through six µ 2 -κN,O:κN′,O-Hbzimed-H ligands. Magnetic studies show that 3 exhibits spin-canting behavior below 10 K, whereas 4 shows only simple antiferromagnetic coupling. Such magnetic behavior of 3 mainly arises from O h -T d mixed geometries of pentameric Co(II) ions, which can result in relatively noncompensated moments, according to different efficient spins of Co(II) at very low temperature and the Dzyaloshinski-Moriya interaction. A discussion of the coordination properties of H 2 bzimed ligands upon different geometries of the central ions, and a probable mechanism for in situ reaction of ligand and the formation of single crystal microtubes is provided.

Molecular structure and conformation in the crystal of N-Boc-Met-Cpg-Phe-OMe, a conformationally restricted tripeptide derivative, structurally related to the chemotactic antagonist agent N-Boc-Met-Leu-Phe-OMe is reported. In the title compound the native central Leu residue has been replaced with the unusual cyclic and achiral quaternary amino acid residue of the 1-aminocyclopent-3-ene-1-carboxylic acid (Cpg). The peptide backbone adopts a type II b-turn (C 10) conformation at the-Met-Cpg-sequence with a distance, between the terminal pseudo-ring atoms O 6 Á Á Á C 3 , of 5.49(1) A. The tripeptide crystallizes in the monoclinic crystal system, space group P2 1 , cell parameter: a ¼ 5.867(7) A, b ¼ 23.54(2) A, c ¼ 10.34(1) A, b ¼ 99.74(5) , V ¼ 1407(2) A 3 ; empirical formula C 26 H 37 N 3 O 6 S; needle crystals were obtained by slow evaporation of an ethyl acetate solution, after 4 days, at room temperature. The low diffraction power of the crystals, it was impossible to obtain crystal structure from normal diffractometer data, suggested to utilize X-ray synchrotron radiation.

The crystal structure of trigonal neodymium trihydride has been refined by neutron powder diffraction on a two-phase deuteride samplē˚(NdD , space group P3c1, a56.6581(2) A, c56.8778(2) A, T5293 K, LaF (tysonite) type structure). The hcp metal atom host structure 3 3c ontains three sorts of deuterium atoms, one occupying tetrahedral interstices with bond distances in the range Nd-D52.36-2.58 A, and two having nearly triangular metal coordinations with bond distances of Nd-D52.24 and 2.26 A. One of the triangular sites is ordered and the other disordered, in contrast to previous work on rare-earth analogues that suggested both sites to be disordered. NdD coexists 3 with a cubic phase of composition NdD in which deuterium atoms occupy tetrahedral and octahedral interstices of a ccp metal atom 2.61h ost structure (space group Fm3m, a55.4324(2) A).

The Li 1.746 Nd 4.494 FeO 9.493 (LNF) ternary phase, located in the Li 2 O-rich part of the Li 2 O-Nd 2 O 3-Fe 2 O 3 system, crystallizes with a cubic unit cell of dimension a ¼ 11:9763ð3ÞÅ and the space group Im3m. Refinement on F resulted in R ¼ 1:9%. The structure is comprised of a network of corners, edges and faces sharing the coordination polyhedra of neodymium. In between this skeleton the regular octahedra of oxygen-coordinated iron and trigonal prisms of lithium are located. The Mo¨ssbauer spectra revealed the presence of Fe 3+ , Fe 4+ and Fe 5+ ions distributed on two symmetry-independent lattice positions.

A single crystal refers to a solid state in which molecules (atoms or ions) contained in the sample are regularly and periodically arranged in a three-dimensional space. A single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries.

Structure D 2000 Crystal Structure of the CeIr 3 Compound.-The structure of the title compound is determined by single crystal XRD for the first time. CeIr 3 crystallizes in the PuNi 3 type structure (space group R3m, Z = 9) and belongs to the Ln 2n+n M 4m+5n family, where m and n are the numbers of MgCu-and CaCu 5-type slabs, resp., and m = n = 1 for CeIr 3 .

Single crystals of Li 0.68 CoO 2 , Li 0.48 CoO 2 , and Li 0.35 CoO 2 were successfully synthesized for the first time by means of electrochemical and chemical delithiation processes using LiCoO 2 single crystals as a parent compound. A single-crystal X-ray diffraction study confirmed the trigonal R3m space group and the hexagonal lattice parameters a ¼ 2.8107(5) Å , c ¼ 14.2235(6) Å , and c/a ¼ 5.060 for Li 0.68 CoO 2 ; a ¼ 2.8090(15) Å , c ¼ 14.3890(17) Å , and c/a ¼ 5.122 for Li 0.48 CoO 2 ; and a ¼ 2.8070(12) Å , c ¼ 14.4359(14) Å , and c/ a ¼ 5.143 for Li 0.35 CoO 2. The crystal structures were refined to the conventional values R ¼ 1.99% and wR ¼ 1.88% for Li 0.68 CoO 2 ; R ¼ 2.40% and wR ¼ 2.58% for Li 0.48 CoO 2 ; and R ¼ 2.63% and wR ¼ 2.56% for Li 0.35 CoO 2. The oxygen-oxygen contact distance in the CoO 6 octahedron was determined to be shortened by the delithiation from 2.6180(9) Å in LiCoO 2 to 2.5385(15) Å in Li 0.35 CoO 2. The electron density distributions of these Li x CoO 2 crystals were analyzed by the maximum entropy method (MEM) using the present singlecrystal X-ray diffraction data at 300 K. From the results of the single-crystal MEM, strong covalent bonding was clearly visible between the Co and O atoms, while no bonding was found around the Li atoms in these compounds. The gradual decrease in the electron density at the Li site upon delithiation could be precisely analyzed.

The high-pressure behavior of kernite [ideally Na 2 B 4 O 6 (OH) 2 •3H 2 O, a ~7.02 Å, b ~9.16 Å, c ~15.68 Å, β = 108.9°, Sp. Gr. P2 1 /c, at ambient conditions], an important B-bearing raw material (with B 2 O 3  51 wt%) and a potential B-rich aggregate in radiation shielding materials, has been studied by single-crystal synchrotron X-ray diffraction up to 14.6 GPa. Kernite undergoes an isosymmetric phase transition at 1.6-2.0 GPa (to kernite-II). Between 6.6-7.5 GPa, kernite undergoes a second phase transition, possibly iso-symmetric in character (to kernite-III). The crystal structure of kernite-II was solved and refined. The isothermal bulk modulus (K V0 = -1 P0,T0 , where  P0,T0 is the volume compressibility coefficient) of the ambient-pressure polymorph of kernite was found to be K V0 = 29(1) GPa and a marked anisotropic compressional pattern, with K(a) 0 : K(b) 0 : K(c) 0 ~ 1:3:1.5., was observed. In kernite-II, the K V0 increase to 43.3(9) GPa and the Accepted Article This article is protected by copyright. All rights reserved anisotropic compressional pattern increases pronouncedly. The mechanisms, at the atomic scale, which govern the structure deformation, have been described.

Pentagonal, octagonal; decagonal and dodecagonal structures have been observed in several alloy systems. These structures are quasiperiodic in a plane and periodic in its perpendicular direction. Crystals aperiodic in one direction have been known for decades. It is interesting to study intermediate structures in which the periodic and quasiperiodi directions are intrinsically connected. That may be done by projecting a a periodic structure in D (>3) dimensions into threedimensional space so that a second projection be quasiperiodic in a plane. We have achieved this earlier in the octagonal case [1] and partly in the dodecagonal case [2]. Here we present an improved dodecagonal version, as well as a new look at the pentagonal, or rather decagonal case. In the dodecagonal case we cut and project first the four-dimensional root lattice D 4 into R 3 and then into a suitable irrational R 2. In the pentagonal/decagonal case we start with the fivedimensional simple cubic lattice Z 5 .

In coordination chemistry; ligands comprising more than single donor sites are broadly used for the research of metal centers with numerous pharmacological activities. Amongst these ligands, Schiff bases comprising hetero atoms as donor atoms are of significant importance due to their possible application in catalysis, medicine and material science [1-5]. The Transition metal centers of these ligands display variable conformations, structural obligation and sensitivity to molecular surroundings. The central metal ions in these developments act as vigorous places for catalyzing chemical reactions. Based on the useful applications on these transition metal complexes in catalytic oxidation reaction number of reports where initiate some reports were oxidation is carried out using molecular oxygen at ambient circumstances. In a series of research done by, Taqui khan et al. reported the catalytic oxidations of olefins, saturated hydrocarbons and amines using Ru (III) EDTA complex and molecular oxygen [6, 7, 8]. Mahesh Dalal et al. experiential that the rate of oxidation of benzyl alcohol improved linearly with growing in substrate concentration by polymer anchored Ru (III) Schiff base compounds and polymer anchored Ru (III) salen complexes [9, 10]. Anthony The odore David stated the catalytic oxidation of Schiff base improved chitosan in the oxidation of cyclohexane [11, 12]. Haresh G. Manyar et al. stated green catalytic oxidation of alcohols in water by very effective mangano silicate molecular sieves. Primary alcohols are

The ternary compound Cu2SnTe3 crystallizes in the Imm2 (Nº 44) space group, Z = 2, with a = 12.833(4) Å, b = 4.274(1) Å, c = 6.043(1) Å, V = 331.5(1) Å3. Its structure was refined from X‐ray powder diffraction data using the Rietveld method. The refinement of 25 instrumental and structural variables led to Rp = 10.2%, Rwp = 11.8%, Rexp = 7.7%, RB = 10.6%, S = 1.6 and χ2 = 2.6, for 5501 step intensities and 163 independent reflections. This compound is isostructural with Cu2GeSe3, and consists of a three‐dimensional arrangement of slightly distorted CuTe4 and SnTe4 tetrahedra connected by common corners. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In this study, both solvent evaporation and hydrothermal methods were employed to grow hydrated sodium borate crystals using NaOH and H 3 BO 3 as reagents, and transparent and colorless single-crystals were successfully obtained with sizes up to 12 Â 6 Â 6 mm 3 and 6 Â 5 Â 4 mm 3 , respectively. The structure is determined by single-crystal X-ray diffraction techniques. The title compound crystallizes in the trigonal space group R32, with a ¼ 11.1042(16) A, b ¼ 11.1042(16) A, c ¼ 21.131(4) A, Z ¼ 9 and R 1 ¼ 0.0322, wR 2 ¼ 0.0840. Infrared and transmission spectra are presented for the reported material. The powder second-harmonic generation (SHG) intensity measured by the Kurtz-Perry method indicates that the SHG effect of Na 2 B 4 O 12 H 10 is about one-third times that of KH 2 PO 4 (KDP).

In this study, both solvent evaporation and hydrothermal methods were employed to grow hydrated sodium borate crystals using NaOH and H 3 BO 3 as reagents, and transparent and colorless single-crystals were successfully obtained with sizes up to 12 Â 6 Â 6 mm 3 and 6 Â 5 Â 4 mm 3 , respectively. The structure is determined by single-crystal X-ray diffraction techniques. The title compound crystallizes in the trigonal space group R32, with a ¼ 11.1042(16) A, b ¼ 11.1042(16) A, c ¼ 21.131(4) A, Z ¼ 9 and R 1 ¼ 0.0322, wR 2 ¼ 0.0840. Infrared and transmission spectra are presented for the reported material. The powder second-harmonic generation (SHG) intensity measured by the Kurtz-Perry method indicates that the SHG effect of Na 2 B 4 O 12 H 10 is about one-third times that of KH 2 PO 4 (KDP).

The ternary nitride La 2 GaN 3 was synthesized from the elements and an excess of sodium and gallium at 900°C in a sealed niobium tube. La 2 GaN 3 is yellow colored and crystallizes with the Ba 2 ZnO 3 structure [monoclinic space group C2/c (No.15), a = 5.6709(5) Å, b = 10.945(1) Å, c = 11.986(1) Å, β = 93.591(5)°, V = 742.54(12) Å 3 , Z = 8] and is isostructural with the A 2 II M V N 3 nitrides, Sr(Ba) 2 TaN 3 , Sr(Ba) 2 NbN 3 , Ca(Sr) 2 VN 3 . The structure contains infinite chains of GaN 4 tetrahedral anions,  1 [GaN 2 N 2/2 ] 6-.

A new interactive software tool is described, that visualizes 3D space group symmetries. The software computes with Clifford (geometric) algebra. The space group visualizer (SGV) originated as a script for the open source visual CLUCalc, which fully supports geometric algebra computation. Selected generators (Hestenes and Holt, JMP, 2007) form a multivector generator basis of each space group. The approach corresponds to an algebraic implementation of groups generated by reflections (Coxeter and Moser, 4th ed., 1980). The basic operation is the reflection. Two reflections at non-parallel planes yield a rotation, two reflections at parallel planes a translation, etc. Combination of reflections corresponds to the geometric product of vectors describing the individual reflection planes. We first give some insights into the Clifford geometric algebra description of space groups. We relate the choice of symmetry vectors and the origin of cells in the geometric algebra description and its implementation in the SGV to the conventional crystal cell choices in the International Tables of Crystallography (T. Hahn, Springer, 2005). Finally we briefly explain how to use the SGV beginning with space group selection. The interactive computer graphics can be used to fully understand how reflections combine to generate all 230 three-dimensional space groups.

We have examined the structure of a Cu 3 Au-type compound CeRh 3 B 0.5 by means of electron diffraction and high-resolution electron microscopy. The observed electron diffraction patterns of CeRh 3 B 0.5 show the appearance of 1/2 1/2 1/2-type superlattice reflections and fine satellite reflections around all reflections. These features have not been detected by X-ray powder diffraction study. The new ordered structure producing the superlattice reflections belongs to a tetragonal system, space group I4/mmm (No. 139) and cell parameters of a t = b t = a c √ 2 = 0.5795 nm and c t = 2c c = 0.8196 nm. The proposed model is characterized by ordering of both B atoms and Rh octahedrons. The observed high-resolution image taken with a diffraction pattern showing the satellite reflections along the [0 1 1] direction shows a domain structure with size of about 3 nm, and a lattice modulation and some edge dislocations have been observed at boundaries between the domains. It is suggested that the anomalous behavior of hardness in CeRh 3 B x is caused by the appearance of this modulated structure.

The title structure, [CuCl(C4H13N3)]Cl, consists of alternating [CuCl(dien)]+ (dien is diethylenetriamine) and Cl- ions arranged in quasi-one-dimensional stacks along the crystallographic a axis and forming tetragonally elongated octahedral coordination shells around each Cu atom [equatorial Cu-Cl = 2.2552 (8) A, and axial Cu-Cl = 2.831 (1) and 3.341 (1) A]. Crystallographic mirror planes bisect each stack vertically through the Cu, Cl and central N atoms, and horizontally through the [CuCl(dien)]+ cation. The horizontal mirrors lead to each atom in the puckered [CuCl(dien)]+ cations being disordered over two crystallographically equivalent sites. Comparison of the title structure with its Br and I analogues shows a growing influence of hydrogen bonding relative to coordination bonds on traversing the series I &lt; Br &lt; Cl.

A single crystal of Al4(Cr,Fe) with composition Al78Cr19Fe3 grown by the Czochralski method was studied by neutron diffraction for the first time. As a preliminary result the neutron diffraction experiment suggests a body-centered orthorhombic space group Immm with a = 1.24985(3) nm, b = 1.25500(3) nm and c = 3.0512(2) nm as found by Deng et al. (Pearson symbol: oI366-59.56) [1] using single crystal X-ray diffraction. Additionally, more or less diffuse maxima at positions with k = n/2 (n = odd) are clearly observable.

The high-pressure behaviour of PbS was investigated by angular dispersive X-ray powder diffraction up to pressures of 6.8 GPa. Experiments were accompanied by first principles calculations at the density functional theory level. By combining both methods reliable data for the elastic properties of rock-salt type α-and high-pressure β-PbS could be obtained. β-PbS could be determined to crystallise in the CrB-type (B33), with space group Cmcm. The reversible ferro-elastic α/β transition is of first order. It is accompanied by a large volume discontinuity of about 5% and a coexistence region of the two phases. A gliding mechanism of {001} bilayers along one of the cubic 110 directions governs the phase transition which can be described in terms of group/subgroup relationships via a common subgroup, despite its reconstructive character. The quadrupling of the primitive unit cell indicates a wave vector (0, 0, π/a) on the ∆-line of the Brillouin zone.

The preparation and crystal structure of a new cocrystal between urea and imidazolidone is reported. An uncharacteristic structural motif of urea molecules was identified and found to be exhibited by only one other urea-containing structure in the Cambridge Structural Database. A comparison is made between the two cocrystals through the use of graph set analysis. The fact that the two structures are of molecules with different H-bonding functionalities did not alter the hydrogen bonding topology but was manifested in slight geometric alterations. The overall structure is structurally dominated by the formation of an identical extended one-dimensional substructure of urea molecules which pack slightly differently, the second component playing the role of a linker. The importance of examining the extended structure, as opposed to only cell constants and space group, when searching for structural similarity, is illustrated. Crystal data: triclinic space group P1 j , a) 5.112(3) Å, b) 7.944(4) Å, c) 9.247(5) Å, R) 85.62(1)°,) 74.92(1)°, γ) 75.35(9)°, V) 350.8(3) Å 3 , Z) 2, D calc) 1.384 Mg/m 3 , µ) 0.112 mm-1 , F(000)) 156, θ min) 2.28 to θ max) 26.36°, R1) 0.0491, wR1) 0.1607 observed data (I > 2σI)) 999, total) 1850, R(int)) 0.023, GOF) 1.13 for 132 parameters.

The preparation and crystal structure of a new cocrystal between urea and imidazolidone is reported. An uncharacteristic structural motif of urea molecules was identified and found to be exhibited by only one other urea-containing structure in the Cambridge Structural Database. A comparison is made between the two cocrystals through the use of graph set analysis. The fact that the two structures are of molecules with different H-bonding functionalities did not alter the hydrogen bonding topology but was manifested in slight geometric alterations. The overall structure is structurally dominated by the formation of an identical extended one-dimensional substructure of urea molecules which pack slightly differently, the second component playing the role of a linker. The importance of examining the extended structure, as opposed to only cell constants and space group, when searching for structural similarity, is illustrated. Crystal data: triclinic space group P1 j , a) 5.112(3) Å, b) 7.944(4) Å, c) 9.247(5) Å, R) 85.62(1)°,) 74.92(1)°, γ) 75.35(9)°, V) 350.8(3) Å 3 , Z) 2, D calc) 1.384 Mg/m 3 , µ) 0.112 mm-1 , F(000)) 156, θ min) 2.28 to θ max) 26.36°, R1) 0.0491, wR1) 0.1607 observed data (I > 2σI)) 999, total) 1850, R(int)) 0.023, GOF) 1.13 for 132 parameters.

This paper introduces a temperature-dependent hysteresis model based on a vectorial elemental operator with temperaturesensitive spontaneous magnetization and biaxial anisotropy for the soft ferrites. Detailed analysis of the temperature-dependent magnetic properties of one elemental operator has been presented thereafter. With the help of the proposed vector elemental operator and the two-dimensional Gaussian distribution function, the temperature-dependent magnetic hysteresis of soft ferrites can be simulated. This model is validated by the substantial agreement between the simulated and measured major hysteresis loops of a soft ferrite sample Siemens 4C65 at different temperatures with slight acceptable error.

Structures and phase transitions for the isostructural series of compounds KFeO 2 , RbFeO 2 and CsFeO 2 have been systematically studied by synchrotron X-ray high resolution powder diffraction experiments and in case of CsFeO 2 also by single crystal diffractometry. At room temperature, all of the three compounds crystallize in the orthorhombic (Pbca) KGaO 2 type of structure consisting of a three dimensional network of corner-sharing [FeO 4/2 ] À tetrahedra, which at elevated temperatures shows a reversible phase transformation to a cubic structure (space group Fd3m). For KFeO 2 , RbFeO 2 and CsFeO 2 this phase transformation takes place at 1003 K, 737 K and 350 K respectively, as confirmed by differential scanning calorimetry and X-ray diffraction. Upon heating through the transitions the major structural changes are driven by the onset or enhancement of librational motion of the FeO 4 tetrahedra. Due to this phenomenon the Fe-O-Fe bonds appear to step-wise getting straight, seemingly approaching 1801 within the time and space averaged structure.

A novel polymorph of the antidepressant drug venlafaxine hydrochloride (VenHCl) was visualized in thermal microscopy and identified by variable-temperature powder X-ray diffraction at 180-190°C. Its single-crystal X-ray structure was solved and refined satisfactorily in P2 1 /n space group (form 6, Z′) 2, T) 100 K, R 1) 0.1073). The powder X-ray diffraction pattern and melting point of form 6 are significantly different from the known polymorphs 1-5. Form 6 has a higher melting point and is more stable than marketed drug forms 1 and 2.

We have adapted the anion chain length model of Cleaver and Sime to predict the distribution of anions in a polysulfide melt, Na2Sx (1-< X-6), as a function of composition the mole fraction of total sulfur. This was then used to calculate the EMF of a Na/S celt from Xs = 0.75 to 0.56, where Xs is the mole fraction of sulfur. This range corresponds to the entire two-phase region. The predicted anion distribution is similar to that of Cleaver and Sime except for the prediction of the appearance of Na2S to high states of discharge; the calculated EMF provides a good fit to the literature values.

New bismuth calcium silicon oxide Ca 4 Bi 4.3 (SiO 4)(HSiO 4) 5 O 0.95 , with apatite structure has been synthesized. The structure was refined from powder X-ray diffraction data. The refinement revealed that the phase has P6 3 /m (176) space group with unit cell parameters a ¼ b ¼9.6090(7)Å, c ¼ 7.0521(7)Å, V¼ 563.9Å 3 and c/a¼ 0.734. The R wp factor at Rietveld refinement was equal to 0.082. The synthesized phase has an unusual quantity of cation vacancies in a crystal lattice. Mechanisms of compensation of the excess charge of a lattice are considered and checked experimentally using the FT-IR spectroscopy, the thermal analysis and the XPS analysis.

Two novel layered germanates, denoted as SU-22 and SU-23, have been synthesized hydro(solvo)thermally by using diethylenetriamine (DETA) and 1,7-diaminoheptane (DAHep) as structure directing agents (SDAs), respectively. Their structures were determined by single-crystal X-ray diffraction. Both structures are built from the same Ge 7 clusters which are 4-coordinated following a 4 4 topology with different modes of linkage. SU-23 is the first example of a different mode leading to the formation of 10-rings, instead of 8-and 12-rings observed in the ASU-20 compounds and SU-22. A third type of linkage is also proposed. The study of the hydrogen bonding interaction pattern is developed to provide insight into the formation of these different modes in relation with the size and geometry of the SDAs, as they have a significant effect on the rotation and arrangements of Ge 7 clusters. SU-22, [C 4 N 3 H 15 ] 1.5 [Ge 7 O 14 X 3 ] • H 2 O (X) OH or F), monoclinic, space group C2/c, a) 16.0583(8), b) 16.4484(10), c) 17.7788(8) Å,) 98.151(6)°, R1) 0.0430, for 4248 reflections with I < 2σ(I). SU-23, [C 7 N 2 H 19 ][C 7 N 2 H 20 ][Ge 7 O 14 X 3 ][GeO 2 ] 0.2 • 3H 2 O, monoclinic, space group P2 1 /n, a) 13.036(3), b) 9.4726(19), c) 30.814(6) Å,) 100.03(3)°, R1) 0.0349 for 5741 reflections with I < 2σ(I).

The CCDC statistics reveal that the P21/c space group is the most common space group found in Cadmium Azide complexes. However, there are several rare space groups present in these compounds, which have not been explored in detail. This mini-review aims to shed light on these uncommon space groups in cadmium azide compounds, including I41/acd, R3̅ , Pcca, and C2/m. Each space group is described in detail, and an example is presented for each to provide a better understanding of their unique properties. For instance, the I41/acd space group has a tetragonal crystal system with a unique four-fold symmetry axis, while the R3̅ space group belongs to the trigonal crystal system and has a threefold axis of symmetry. Cd(N3)2 is used as an example for each space group to illustrate their characteristics. These findings offer valuable insights into exploring uncommon space groups in cadmium azide compounds, which could lead to the creation of new materials with unique properties. This research could have significant implications for the development of advanced materials in various fields, including electronics, optics, and catalysis.

Sr 2 Co 2 O 5 with the perovskite-related brownmillerite structure has been synthesised via quenching, with the orthorhombic unit cell parameters a ¼ 5.4639(3)Å, b ¼ 15.6486(8)Å and c¼ 5.5667(3)Å based on refinement of neutron powder diffraction data collected at 4 K. Electron microscopy revealed L-R-L-R-intralayer ordering of chain orientations, which require a doubling of the unit cell along the c-parameter, consistent with the assignment of the space group Pcmb. However, on the length scale pertinent to NPD, no long-range order is observed and the disordered space group Imma appears more appropriate. The magnetic structure corresponds to G-type order with a moment of 3.00(4) m B directed along [1 0 0].

The crystal structure of PA5185, a putative thioesterase from Pseudomonas aeruginosa strain PAO1, was solved using multi-wavelength anomalous diffraction to 2.4 Å. Analysis of the structure and information about the putative function of the protein were used to optimize crystallization conditions. The crystal growth was optimized by applying additives with chemical similarity to a fragment of a putative PA5185 substrate (CoA or its derivative). Using new crystallization conditions containing this function-biased set of additives, several new crystal forms were produced and structures of three of them (in three different space groups) were determined. One of the new crystal forms had an improved resolution limit of 1.9 Å, and another displayed an alternative conformation of the highly-conserved loop containing Asn26, which could play a physiological role. Surprisingly, none of the additives were ordered in the crystal structures. Application of function-biased additives could be used as a standard optimization protocol for producing improved diffraction, or new crystal forms, which may lead to better understanding of the biological functions of proteins.

The present investigation deals with synthesis and gas sensing performance of Na 8 [AlSiO 4 ] 6 (N 3) 2.4 (H 2 O) 4.6 cancrinite-based thick film. The product obtained was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, thermogravimetric analysis and magic-angle spin nuclear magnetic resonance (MAS NMR). The crystal structure of the product was determined from X-ray powder diffraction data by applying Rietveld refinement. Refinement showed that azide cancrinite crystallize in the space group P6 3. Alternate arrangement of Si and Al atoms was confirmed by single intense peak of MAS NMR analysis. For the first time, this study reports the gas sensing performance of aluminosilicate azide cancrinite. The effect of annealing and operating temperature on gas sensing characteristic of azide cancrinite thick film is investigated systematically for various gases at different operating temperatures. This sensor was observed to be highly sensitive and selective to ammonia gas.

Imines obtained by condensation of 4-hydroxybenzohydrazide with aliphatic ketones are a rare example of a class of compounds showing a remarkable tendency to crystallize in acentric polar space groups (Pna2 1 or Cc). In fact, all of the (seven) compounds studied up to now show at least one polar polymorph. In some cases, polymorphism was detected, and a nonpolar centrosymmetric phase was also identified (P2 1 /c or P2 1 /n space group). With the aim to disclose the conditions that can favor the formation of acentric structures in molecular crystals, we report, in this paper, a theoretical analysis (ab initio density functional theory with periodic boundary) of the lattice energy and density of all the packing modes observed in the whole set of imines. The computational analysis has been performed by optimizing each compound in its own experimental packings (actual crystal structures) and also in the packings of the other compounds of the class (virtual structures). The experimental crystallographic data and the theoretical analysis suggest that two conformers, basically differing for the orientation of the phenolic H atom in the plane of the phenyl ring, compete, in solution, for the formation of polar or centrosymmetric packings. The transitions between polar and centrosymmetric polymorphs are of diffusive type, and single crystals are not preserved, while the transitions between different polar polymorphs can be of singlecrystal-to-single-crystal type.

Sm, Gd) have been prepared by a Pechini sol-gel process using lanthanide nitrates and telluric acid as precursors. All samples were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Raman and Fourier transform infrared spectroscopy (FT-IR), as well as thermogravimetric analysis (TG). The AFM study reveals that the samples consist of particles with average crystal size ranging from 70 to 110 nm. The results of X-ray diffraction indicate that Ln 2 TeO 6 (Ln = Y, La, Sm, Gd) crystallize isotypically with the orthorhombic La 2 TeO 6 in the space group P2 1 2 1 2 1. The infrared and Raman spectra show that the TeO 6 groups are independent vibrating groups and the results obtained were discussed on the basis of the site symmetry analysis derivates from the structural data.

In this work, an investigation on the polymorphism of trans-1,4-cyclohexanediol is performed. Polymorph screening is carried out by crystallization from solutions, by sublimation, and by cooling the melt, and a combined approach using differential scanning calorimetry, polarized light thermomicroscopy, and X-ray diffraction is employed in the results interpretation. Three solid forms, I, II, and III (Steiner et al. J. Chem. Soc., Perkin Trans. 2 1998, 371-377), are identified, I and II, for the first time, and their relative stability established. The crystal structure of polymorph II is resolved by single crystal X-ray diffraction: a monoclinic P2 1 /a space group structure. This polymorph, as polymorph III (Steiner et al. J. Chem. Soc., Perkin Trans. 2 1998, 371-377), exhibits unusual conformational isomorphism, that is, the coexistence of the biequatorial and the biaxial conformers in the same crystal structure.

Source of material: Synthesis from the elements by arc melting and annealing at 773 Κ in evacuated quartz tubes for 3 weeks. Nominal composition Zr66.7FeiuAl22.2. Data reduction, structure solution and refinement used programs from Xtal3.2 system (see ref. 3). Analytical absorption correction used LSABS (see ref. 4). The atomic coordinates are standardized by STRUCTURE TIDY (see ref. 5). The title compound was reported (see ref. 1) to crystallise with the K2UF6 structure type (see ref. 2). However, no structure refinement has been performed. Our single crystal X-ray study confirms that structure type, and yields refined atomic parameters.