Experimental and theoretical morphologies of diuron, N'-(3,4-dichlorophenyl)-N,N-dimethylurea

1996 ◽  
Vol 52 (4) ◽  
pp. 662-667 ◽  
Author(s):  
G. Pfefer ◽  
R. Boistelle
Keyword(s):  
Crystal Structures ◽  
Crystal Morphology ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Good Agreement ◽  
Attachment Energy

Crystals of diuron, N′-(3,4-dichlorophenyl)-N,N-dimethylurea, C9H10Cl2N2O, were grown from ethanol at low supersaturation. The crystal faces were indexed using a two-circle optical goniometer and X-ray diffraction was used to orientate the crystal morphology with respect to the unit cell. The experimental morphologies were compared with the morphologies predicted by the BFDH (Bravais, Friedel, Donnay, Harker) and attachment energy (AE) methods and calculated from two crystal structures. Good agreement was obtained between experimental and theoretical habits, despite the fact that the crystals exhibit 27 faces belonging to 13 crystallographic forms.

The structures of marialite (Me6) and meionite (Me93) in space groups P42/n and I4/m, and the absence of phase transitions in the scapolite series

2011 ◽  
Vol 26 (2) ◽  
pp. 119-125 ◽  
Author(s):  
Sytle M. Antao ◽  
Ishmael Hassan
Keyword(s):  
Phase Transitions ◽  
High Resolution ◽  
Crystal Structures ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Space Groups ◽  
Cell Parameters ◽  
The Mean

The crystal structures of marialite (Me6) from Badakhshan, Afghanistan and meionite (Me93) from Mt. Vesuvius, Italy were obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. Their structures were refined in space groups I4/m and P42/n, and similar results were obtained. The Me6 sample has a formula Ca0.24Na3.37K0.24[Al3.16Si8.84O24]Cl0.84(CO3)0.15, and its unit-cell parameters are a=12.047555(7), c=7.563210(6) Å, and V=1097.751(1) Å3. The average ⟨T1-O⟩ distances are 1.599(1) Å in I4/m and 1.600(2) Å in P42/n, indicating that the T1 site contains only Si atoms. In P42/n, the average distances of ⟨T2-O⟩=1.655(2) and ⟨T3-O⟩=1.664(2) Å are distinct and are not equal to each other. However, the mean ⟨T2,3-O⟩=1.659(2) Å in P42/n and is identical to the ⟨T2′-O⟩=1.659(1) Å in I4/m. The ⟨M-O⟩ [7]=2.754(1) Å (M site is coordinated to seven framework O atoms) and M-A=2.914(1) Å; these distances are identical in both space groups. The Me93 sample has a formula of Na0.29Ca3.76[Al5.54Si6.46O24]Cl0.05(SO4)0.02(CO3)0.93, and its unit-cell parameters are a=12.19882(1), c=7.576954(8) Å, and V=1127.535(2) Å3. A similar examination of the Me93 sample also shows that both space groups give similar results; however, the C–O distance is more reasonable in P42/n than in I4/m. Refining the scapolite structure near Me0 or Me100 in I4/m forces the T2 and T3 sites (both with multiplicity 8 in P42/n) to be equivalent and form the T2′ site (with multiplicity 16 in I4/m), but ⟨T2-O⟩ is not equal to ⟨T3-O⟩ in P42/n. Using different space groups for different regions across the series implies phase transitions, which do not occur in the scapolite series.

scholarly journals The crystal structures of two polyamides (‘nylons’)

1947 ◽  
Vol 189 (1016) ◽  
pp. 39-68 ◽  
Keyword(s):  
Crystal Structures ◽  
Unit Cell ◽  
Chain Molecule ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Dimensions ◽  
C Fibre ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions ◽  
Crystalline Forms

Detailed interpretations of the X -ray diffraction patterns of fibres and sheets of 66 and 6.10 polyamides (polyhexam ethylene adipamide and sebacamide respectively) are proposed. The crystal structures of the two substances are completely analogous. Fibres of these two polyam ides usually contain two different crystalline forms, α and β, which are different packings of geometrically similar molecules; most fibres consist chiefly of the α form. In the case of the 66 polymer, fibres have been obtained in which there is no detectable proportion of the β form. Unit cell dimensions and the indices of reflexions for the α form were determined by trial, using normal fibre photographs, and were checked by using doubly oriented sheets set at different angles to the X -ray beam. The unit cell of the a form is triclinic, with a — 4·9 A, b = 5·4 A, c (fibre axis) = 17·2A, α = 48 1/2º, β = 77º, γ = 63 1/2º for the 66 polymer; a = 4·95A, b = 5·4A, c (fibre axes) = 22·4A, α = 49º, β = 76 1/2º, γ = 63 1/2º for the 6.10 polymer. One chain molecule passes through the cell in both cases. Atomic coordinates in occrystals were determined by interpretation of the relative intensities of the reflexions. The chains are planar or very nearly so; the oxygen atoms appear to lie a little off the plane of the chain. The molecules are linked by hydrogen bonds between C = 0 and NH groups, to form sheets. A simple packing of these sheets of molecules gives the α arrangement.

Crystal Structures of the Pentacoordinate Bromo, Isocyanato, Iodo, Acetato and Isothiocyanato Complexes of the meso-Tetraphenylporphyrinatomanganese Cation

1998 ◽  
Vol 51 (9) ◽  
pp. 835 ◽  
Author(s):  
Peter Turner ◽  
Maxwell J. Gunter ◽  
Brian W. Skelton ◽  
Allan H. White
Keyword(s):  
Crystal Structures ◽  
Metal Ion ◽  
Crystal Packing ◽  
Carbonyl Oxygen ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Complex Molecules ◽  
X Ray ◽  
Rigid Body Model ◽  
Pyrrole Nitrogen

The room-temperature single-crystal X-ray diffraction determined structures of the Mn(tpp)Br.C7H8, Mn(tpp)(NCO), Mn(tpp)I.C7H8, Mn(tpp)(CO2CH3).0·5C7H8, and Mn(tpp)(NCS).0·5C7H8 complexs are described. The monoclinic P21/c unit cell of Mn(tpp)(NCO) has a 14·82(1), b 17·136(5), c 14·576(5) Å, β 111·41(5)°, V 3446(3) Å3, Z 4. The refinement converged with conventional R(|F|) 0·053 for No 3199 (I > 3·0σ(I)) ‘observed’ reflections. The monoclinic P 21/m unit cell of Mn(tpp)Br.C7H8 has a 9·984(1), b 15·453(6), c 13·583(3) Å, β 103·99(2)°, V 2033(1) Å3, Z 2, R 0·039 for No 2668. The Mn(tpp)I.C7H8 structure is triclinic, P-1, with a 22·28(1), b 14·466(4), c 13·555(6) Å, α 76·32(3), β 81·74(4), γ 74·75(3)°, V 4079(3) Å3, Z 4, R 0·050 for No 9039. The triclinic P-1 crystal structures of the Mn(tpp)(CO2CH3).0·5C7H8 and Mn(tpp)(NCS).0·5C7H8 complexes are isomorphous. The Mn(tpp)(CO2CH3).0·5C7H8 structure has a 26·18(1), b 13·503(3), c 12·074(6) Å, α 66·08(4), β 81·36(4), γ 86·71(5)°, V 3858(3) Å3, Z 4, R 0·075 for No 6388. Solvate disorder, requiring a rigid body model, islargely responsible for the relatively high residuals. The Mn(tpp)(NCS).0·5C7H8 structure has a 25·442(6), b 13·746(3), c 12·182(5) Å, α 66·97(3), β 78·59(3), γ 87·90(2)°, V 3839(2) Å3, Z 4, R 0·061 for No 5506. The asymmetric units of the iodo, acetato and isothiocyanato structures each contain two crystallographically independent complex molecules that are sensitive to crystal packing forces. The metal ion displacements from the least-squares planes formed by the pyrrole nitrogen atoms are 0·299(1) and 0·274(1) Å for the Mn(tpp)(NCO) and Mn(tpp)Br.C7H8complexes, and 0·240(1) and 0·252(1), 0·281(1) and 0·278(1), and 0·243(1) and 0·244(1) Å for the independent (a) and (b) complex molecules of Mn(tpp)I.C7H8, Mn(tpp)(CO2CH3).0·5C7H8, and Mn(tpp)(NCS).0·5C7H8 respectively. The axial Mn–X bond lengths are 2·029(5) and 2·490(1) Å for the Mn(tpp)(NCO) and Mn(tpp)Br.C7H8 complexes, and 2·767(1) and 2·730(1), 2·028(5) and 2·010(5), and 2·067(6) and 2·072(5) Å for the (a) and (b) complex molecules of Mn(tpp)I.C7H8, Mn(tpp)(CO2CH3).0·5C7H8, and Mn(tpp)(NCS).0·5C7H8. One of the independent complex molecules in the Mn(tpp)(CO2CH3).0·5C7H8 structure appears to exhibit acetate coordination through a carbonyl oxygen.

William Barlow’s early publications in the ‘Zeitschrift für Krystallographie und Mineralogie’ and their influence on crystal structure research

2019 ◽  
Vol 234 (11-12) ◽  
pp. 769-785 ◽  
Author(s):  
Peter Paufler
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Crystal Morphology ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Starting Point ◽  
Diffraction Patterns ◽  
Structure Research

AbstractThe English crystallographer William Barlow is famous for two achievements, both published in German, in Zeitschrift für Krystallographie und Mineralogie between 1894 and 1901. They concern the derivation of all possible symmetrical arrangements of points in space and the idea to represent crystal structures by replacing points by spheres. His results had an impact upon crystal structure modelling and describing crystal morphology. Utilizing self-made models, he found the 230 space group types of symmetry obtained earlier by both E. S. Fedorow and A. Schoenflies in a different manner. The structures he proposed before the discovery of X-ray diffraction served in some cases as starting point for the interpretation of diffraction patterns thereafter.

Powder-Pattern: A System of Programs for Processing and Interpreting Powder Diffraction Data

1982 ◽  
Vol 26 ◽  
pp. 63-72 ◽  
Author(s):  
Nikos P. Pyrros ◽  
Camden R. Hubbard
Keyword(s):  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Pure Phase ◽  
Diffraction Patterns ◽  
Better Than ◽  
Good Agreement

The production of standard x-ray diffraction patterns at NBS imposes special requirements in the data processing of powder patterns. The patterns should be complete and have an overall accuracy of better than 0.01 degree two theta. To ensure completeness all the observable peaks should be indexed. To make certain that the sample is a pure phase, weak peaks have to be identified as well.The indexing of all the peaks implies that the cell constants must be known and there should be a good agreement between all the calculated and observed peak positions. In practice this is achieved by a least-squares refinement of the unit cell parameters. This serves as a test of the assumed unit cell and also as an interpretation of the observed peaks. Finally, an attempt is made to identify the space group. This step also requires the identification of weak peaks. The agreement of a known space group with the observed reflections further confirms the purity of the sample.

Structural Study of the Disordered RECd6 Quasicrystal Approximants (RE = Tb, Ho, Er, Tm and Lu)

2006 ◽  
Vol 61 (6) ◽  
pp. 644-649 ◽  
Author(s):  
Shu Ying Piao ◽  
Cesar P. Gömez ◽  
Sven Lidin
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Structural Study ◽  
Diffraction Data ◽  
Unit Cell Dimension ◽  
Unit Cell ◽  
Cell Dimension ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Types

The crystal structures of approximants RECd6 (RE = Tb, Ho, Er, Tm and Lu) have been refined from single crystal X-ray diffraction data. This work is a continuation of a previous study of MCd6 approximants [1] in which the different types of disorder of the central Cd4 tetrahedra located in the dodecahedral cavities were examined. The structures of the title compounds are all similar to GdCd6 and disorder was observed in all these compounds. There is a correlation between the anisotropic displacement parameter and the unit cell dimension

Studies on chitan (β-(1 → 4)-linked 2-acetamido-2-deoxy-D-glucan) fibers of the diatom Thalassiosira fluviatilis, Hustedt. III. The structure of chitan from x-ray diffraction and electron microscope observations

1968 ◽  
Vol 46 (9) ◽  
pp. 1513-1521 ◽  
Author(s):  
N. E. Dweltz ◽  
J. Ross Colvin ◽  
A. G. McInnes
Keyword(s):  
Electron Microscope ◽  
Cross Section ◽  
Three Dimensional ◽  
Unit Cell ◽  
Dimensional Structure ◽  
Polymeric Chain ◽  
X Ray Diffraction ◽  
Screw Axis ◽  
X Ray ◽  
Good Agreement

The form and crystal structure of the fibers attached to the diatom Thalassiosira fluviatilis were studied by the electron microscope and x-ray diffraction.These fibers, which were shown previously to be pure, highly crystalline β-(1 → 4) linked poly-N-acetyl-D-glucosamine (chitan), are strap-like in cross section, 1000–2000 Å in width at their widest point close to the base, from which they taper uniformly to a very small tip at their outer extremity. Three connected filaments or microfibrils form the fiber at its widest point.The unit cell of chitan is monoclinic with the space group P21. The parameters of the unit cell are a = 4.80, b = 10.32, c = 9.83 Å, and β = 112°. The density of the chitan fibers is 1.495 g/cm3. There is only one polymeric chain per unit cell with a two-fold screw axis and therefore the chains are parallel to each other. A three-dimensional structure is proposed for chitan which is reasonable from stereochemical considerations and which is in good agreement with all observed x-ray diffraction data.

scholarly journals Synthesis, Characterization and Biological Studies of Ether–Based Ferrocenyl Amides and their Organic Analogues

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 480
Author(s):  
Sana Waseem Abbasi ◽  
Naveed Zafar Ali ◽  
Martin Etter ◽  
Muhammad Shabbir ◽  
Zareen Akhter ◽  
...  
Keyword(s):  
Single Crystal ◽  
Cell Volume ◽  
Crystal Structures ◽  
Unit Cell Volume ◽  
Unit Cell ◽  
Spectral Studies ◽  
Scavenging Activity ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray

Ferrocenyl amides (FB1-FB13) and their organic analogues (BZ1-BZ13) were prepared by a low-temperature condensation method. Ferrocenyl amides were synthesised using 4-ferrocenylbenzoyl chloride and ether-based amines and diamines. Benzoyl chloride was used to synthesise organic analogues by reacting with various amines. The synthesised compounds were characterised by elemental, spectroscopic (FT-IR and NMR) and single crystal X-ray diffraction methods. Crystal structures of the representative organic analogues (BZ2 and BZ6) were solved by single crystal X-ray diffraction. BZ2 crystallises in the triclinic space group P 1 ¯ with a unit cell volume of V = 1056.6(3) Å3 and with two formula units per unit cell. Whereas BZ6 assembles in the orthorhombic space group Pbca with four formula units per unit cell and a unit cell volume of V = 1354.7(2) Å3. Spectral studies confirmed the presence of amide linkages in the synthesised compound with a strong N—H·····O=C hydrogen bonding network established between amide groups of neighbouring molecular scaffolds further stabilising the molecular stacking in accordance with the archetypal crystal structures. The bioactive nature of each compound was assessed by DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity, hydrogen peroxide scavenging activity and total antioxidant activity. Antidiabetic, anticholinesterase enzyme inhibition tests, as well as antibacterial activities, were performed showing significant biological activity for ferrocenyl amides as compared to their organic analogues.

scholarly journals Crystal structures of synthetic 7 Å and 10 Å manganates substituted by mono- and divalent cations

1994 ◽  
Vol 58 (392) ◽  
pp. 425-447 ◽  
Author(s):  
Kenshi Kuma ◽  
Akira Usui ◽  
William Paplawsky ◽  
Benjamin Gedulin ◽  
Gustaf Arrhenius
Keyword(s):  
Crystal Structures ◽  
Diffraction Data ◽  
Divalent Cations ◽  
Unit Cell ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Monoclinic Crystal ◽  
X Ray ◽  
Cell Parameters

AbstractThe crystal structures of synthetic 7 Å and 10 Å manganates, synthetic birnessite and buserite, substituted by mono- and divalent cations were investigated by X-ray and electron diffractions. The monoclinic unit cell parameters of the subcell of lithium 7 Å manganate, which is one of the best ordered manganates, were obtained by computing the X-ray powder diffraction data: a = 5.152 Å, b = 2.845 Å, c = 7.196 Å, β = 103.08°. On the basis of the indices obtained by computing the X-ray diffraction data of Li 7 Å manganate, monovalent Na, K and Cs and divalent Be, Sr and Ba 7 Å manganates were interpreted as the same monoclinic structure with β = 100–103° as that of Li 7 Å manganate, from their X-ray diffraction data. In addition, divalent Mg, Ca and Ni 10 Å manganates were also interpreted as the same monoclinic crystal system with β = 90–94° The unit cell parameters, especially a, c and β, change possibly with the type of substituent cation probably because of the different ionic radius, hydration energy and molar ratio of substituent cation to manganese. However, these diffraction data, except for those of Sr and Ba 7 Å and Ca and Ni 10 Å manganates, reveal only some parts of the host manganese structure with the edge-shared [MnO6] octahedral layer. On the other hand, one of the superlattice reflections observed in the electron diffractions was found in the X-ray diffraction lines for heavier divalent cations Sr and Ba 7 Å and Ca and Ni 10 Å manganates. The reflection presumably results from the substituent cation position in the interlayer which is associated with the vacancies in the edge-shared [MnO6] layer and indicates that the essential vacancies are linearly arranged parallel to the b-axis. Furthermore, the characteristic superlattice reflection patterns for several cations, Li, Mg, Ca, Sr, Ba and Ni, manganates were interpreted that the substituent cations are regularly distributed in the interlayer according to the exchange percentage of substituent cation to Na+. In contrast, the streaking in the a-direction observed strongly in the electron diffractions for heavier monovalent cations, K and Cs, manganates probably results from the disordering of their cations in the a-direction in the interlayer.

Powder X-ray diffraction study of LaCo0.5Ni0.5O3−δ and LaCo0.5Fe0.5O3−δ

2003 ◽  
Vol 18 (2) ◽  
pp. 159-161 ◽  
Author(s):  
N. P. Vyshatko ◽  
V. V. Kharton ◽  
A. L. Shaula ◽  
F. M. B. Marques
Keyword(s):  
Diffraction Study ◽  
Crystal Structures ◽  
Solid Solutions ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

The crystal structures of LaCo0.5Ni0.5O3−δ and LaCo0.5Fe0.5O3−δ solid solutions, studied by powder X-ray diffraction, were found to be rhombohedral perovskite. The unit cell parameters in the hexagonal setting are a=5.491(6) Å and c=13.231(3) Å for LaCo0.5Fe0.5O3−δ, and a=5.464(4) Å and c=13.125(3) Å for LaCo0.5Ni0.5O3−δ. The space group is R3c (No. 167).

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