Structure determination of the stable anhydrous phase of α-lactose from X-ray powder diffraction

2005 ◽  
Vol 61 (2) ◽  
pp. 185-191 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Frederic Affouard ◽  
Jean-François Willart ◽  
Patrick Derollez ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Room Temperature ◽  
Structural Model ◽  
Hydroxyl Groups ◽  
Rietveld Refinements ◽  
X Ray ◽  
Hydrogen Bond Networks ◽  
Monte Carlo Simulated Annealing ◽  
Annealing Method

The stable anhydrous form of α-lactose has been obtained by the dehydration of α-lactose monohydrate in methanol. An X-ray powder diffraction pattern was recorded at room temperature with a laboratory diffractometer equipped with an INEL curved sensitive detector CPS120. The starting structural model of this form was found by a Monte-Carlo simulated annealing method. The structure was obtained through Rietveld refinements and the minimization of crystalline energy for the localization of the H atoms of the hydroxyl groups. Soft restraints were applied to bond lengths and angles. Networks of O—H...O hydrogen bonds account for the crystalline cohesion. A comparison is made between the hydrogen-bond networks of this form and those of the monohydrate and hygroscopic anhydrous forms of α-lactose.

Structure determination of L-arabinitol by powder X-ray diffraction

2012 ◽  
Vol 68 (4) ◽  
pp. 407-411 ◽  
Author(s):  
Patrick Derollez ◽  
Yannick Guinet ◽  
Frédéric Affouard ◽  
Florence Danède ◽  
Laurent Carpentier ◽  
...  
Keyword(s):  
Structural Model ◽  
Interatomic Bond ◽  
Hydroxyl Groups ◽  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
X Ray ◽  
Monte Carlo Simulated Annealing ◽  
Diffraction Patterns ◽  
Annealing Method

Powder X-ray diffraction patterns of the commercial phase of L-arabinitol were recorded with a laboratory diffractometer. The starting structural model was found by a Monte-Carlo simulated annealing method. The final structure was obtained through Rietveld refinements with soft restraints on the interatomic bond lengths and bond angles. H atoms of hydroxyl groups were localized by minimization of the crystalline energy. The cell is triclinic with the space group P1 and contains two molecules. The crystalline cohesion is achieved by an important network of O—H...O hydrogen bonds.

Structure determination of the 1/1 α/β mixed lactose by X-ray powder diffraction

2005 ◽  
Vol 61 (4) ◽  
pp. 455-463 ◽  
Author(s):  
Jacques Lefebvre ◽  
Jean-François Willart ◽  
Vincent Caron ◽  
Ronan Lefort ◽  
Frédéric Affouard ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Size Effects ◽  
Room Temperature ◽  
Real Space ◽  
Hydroxyl Groups ◽  
Soft Constraints ◽  
Rietveld Refinements ◽  
X Ray ◽  
Mixed Compound

The mixed form of α/β lactose was obtained by heating amorphous α-lactose at 443 K. NMR spectroscopy determined the stoichiometry of this mixed compound to be 1/1. The X-ray powder diffraction pattern was recorded at room temperature with a sensitive curved detector (CPS 120). The structure was solved by real-space methods (simulated annealing) followed by Rietveld refinements with soft constraints on bond lengths and bond angles. The H atoms of the hydroxyl groups were localized by minimization of the crystalline energy. The cell of 1/1 α/β lactose is triclinic with the space group P1 and contains two molecules (one molecule of each anomer). The crystalline cohesion is achieved by networks of O—H...O hydrogen bonds. The width of the Bragg peaks is interpreted through a microstructural approach in terms of isotropic strain effects and anisotropic size effects.

Ab initio structure determination of the hygroscopic anhydrous form of α-lactose by powder X-ray diffraction

2004 ◽  
Vol 60 (4) ◽  
pp. 453-460 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Frederic Affouard ◽  
Patrick Derollez
Keyword(s):  
Structural Model ◽  
Interatomic Bond ◽  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
X Ray ◽  
Ab Initio Structure ◽  
Monte Carlo Simulated Annealing ◽  
Hydroxy Groups ◽  
Annealing Method

Annealing of α-lactose monohydrate at 408 K yielded a mixture of this compound with hygroscopic anhydrous α-lactose. A powder X-ray diffraction pattern of this mixture was recorded at room temperature. The starting structural model of hygroscopic α-lactose was found by a Monte Carlo simulated-annealing method. The final structure was obtained through Rietveld refinements, with soft restraints on interatomic bond lengths and bond angles, and crystalline energy minimization to locate the H atoms of the hydroxy groups. The crystalline cohesion is achieved by networks of O—H...O hydrogen bonds that differ from those of the monohydrate phase. The width of the Bragg peaks is interpreted by a phenomenological microstructural approach in terms of isotropic size effects and anisotropic strain effects.

Structure determination of forms I and II of phenobarbital from X-ray powder diffraction

2005 ◽  
Vol 61 (1) ◽  
pp. 80-88 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Stephanie Hemon ◽  
Carsten Baehtz ◽  
Florence Danede ◽  
...  
Keyword(s):  
X Ray Diffraction ◽  
Rietveld Refinements ◽  
Space Group ◽  
X Ray ◽  
Bragg Peak Profiles ◽  
Monte Carlo Simulated Annealing ◽  
Crystal Structural ◽  
Diffraction Patterns ◽  
Annealing Method

From pure powders of forms I and II of phenobarbital, X-ray diffraction patterns were recorded at room temperature. The starting crystal structural models were found by a Monte-Carlo simulated annealing method. The structures of the two forms were obtained through Rietveld refinements. Soft restraints were applied on bond lengths and bond angles, all H-atom positions were calculated. The cell of form I is monoclinic with the space group P21/n, Z = 12, Z′ = 3. Form II has a triclinic cell, with the space group P\bar 1, Z = 6, Z′ = 3. For both forms, the crystal cohesion is achieved by networks of N—H...O hydrogen bonds along [101]. The broadening of the Bragg peak profiles is interpreted in terms of isotropic strain effects and anisotropic size effects.

Distorted chiolite crystal structures of α-Na5M3F14 (M=Cr,Fe,Ga) studied by X-ray powder diffraction

2003 ◽  
Vol 18 (2) ◽  
pp. 128-134 ◽  
Author(s):  
A. Le Bail ◽  
A.-M. Mercier
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Rietveld Refinements ◽  
Space Group ◽  
X Ray ◽  
Precise Characterization

The crystal structures of the chiolite-related room temperature phases α-Na5M3F14 (MIII=Cr,Fe,Ga) are determined. For all of them, the space group is P21/n, Z=2; a=10.5096(3) Å, b=7.2253(2) Å, c=7.2713(2) Å, β=90.6753(7)° (M=Cr); a=10.4342(7) Å, b=7.3418(6) Å, c=7.4023(6) Å, β=90.799(5)° (M=Fe), and a=10.4052(1) Å, b=7.2251(1) Å, c=7.2689(1), β=90.6640(4)° (M=Ga). Rietveld refinements produce final RF factors 0.036, 0.033, and 0.035, and RWP factors, 0.125, 0.116, and 0.096, for MIII=Cr, Fe, and Ga, respectively. The MF6 polyhedra in the defective isolated perovskite-like layers deviate very few from perfect octahedra. Subtle octahedra tiltings lead to the symmetry decrease from the P4/mnc space group adopted by the Na5Al3F14 chiolite aristotype to the P21/n space group adopted by the title series. Facile twinning precluded till now the precise characterization of these compounds.

Ab initiostructure determination of the Γ form ofD-sorbitol (D-glucitol) by powder synchrotron X-ray diffraction

2004 ◽  
Vol 37 (5) ◽  
pp. 766-772 ◽  
Author(s):  
Mwaffak Rukiah ◽  
Jacques Lefebvre ◽  
Olivier Hernandez ◽  
Wouter van Beek ◽  
Michel Serpelloni
Keyword(s):  
Monte Carlo ◽  
Simulated Annealing ◽  
Interatomic Bond ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Rietveld Refinements ◽  
X Ray ◽  
Monte Carlo Simulated Annealing ◽  
Starting Model

A high-resolution powder synchrotron X-ray diffraction pattern of the Γ form of D-sorbitol has been recorded at 293 K on the BM1B beamline at the ESRF (Grenoble). The starting model of the structure was found by Monte Carlo simulated annealing. The final structure was obtained through Rietveld refinements performed with soft restraints on interatomic bond lengths and angles. The symmetry is orthorhombic, space groupP21212, with 12 molecules within the cell [a= 24.3012 (2),b= 20.5726 (2),c= 4.8672 (1) Å,V= 2433.30 (3) Å3,Z′ = 3, 36 non-H independent atoms]. Crystalline cohesion between neighbouring molecules is achieved by three networks of O—H...O hydrogen bonds. The width of the Bragg peaks is interpreted through a microstructural approach in terms of anisotropic strain effects.

Determination of crystal structures and tautomeric states of 2-ammoniobenzenesulfonates by laboratory X-ray powder diffraction

2015 ◽  
Vol 230 (9-10) ◽  
Author(s):  
Sándor L. Bekö ◽  
Christian Czech ◽  
Marcus A. Neumann ◽  
Martin U. Schmidt
Keyword(s):  
Dft Calculations ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Laboratory Data ◽  
Powder Diffraction Data ◽  
Dft Methods ◽  
Rietveld Refinements ◽  
X Ray ◽  
Polymorph Screening

AbstractThe crystal structures of 4-chloro-5-methyl-2-ammoniobenzenesulfonate and of the corresponding derivatives 4,5-dimethyl- and 4,5-dichloro-2-ammoniobenzenesulfonates have been determined from laboratory X-ray powder diffraction data. The tautomeric state of all three compounds could also be unequivocally determined from laboratory data, using careful Rietveld refinements. The tautomeric state was confirmed by IR spectroscopy. The compounds are neither isostructural to each other nor to the 5-chloro-4-methyl derivate, despite the similar size of the chloro and methyl substituents. The influence of the chloro and methyl substituents on the packing and on the thermal stability is demonstrated. All crystal structures were confirmed by dispersion-corrected DFT calculations. For the 4-chloro-5-methyl and the 4,5-dichloro derivatives the DFT calculations indicated that the observed polymorph should not be the thermodynamical one. However, no other polymorphs could be found in experimental polymorph screening, even using seeding with the corresponding isostructural phases. Obviously the DFT methods need further improvements.

Structure determination of phase II of the antifungal drug griseofulvin by powder X-ray diffraction

2018 ◽  
Vol 74 (3) ◽  
pp. 321-324 ◽  
Author(s):  
Aurélien Mahieu ◽  
Jean-François Willart ◽  
Mathieu Guerain ◽  
Patrick Derollez ◽  
Florence Danéde ◽  
...  
Keyword(s):  
Phase Ii ◽  
Structural Model ◽  
Interatomic Bond ◽  
Antifungal Drug ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Pxrd Pattern ◽  
X Ray ◽  
Monte Carlo Simulated Annealing

Two new crystalline polymorphs of the widely used antifungal drug griseofulvin (phases II and III), which originate from the crystallization of the melt, have been detected recently. The crystal structure of phase II of griseofulvin {systematic name: (2S,6′R)-7-chloro-2′,4,6-trimethoxy-6′-methyl-3H,4′H-spiro[1-benzofuran-2,1′-cyclohex-2-ene]-3,4′-dione}, C17H17ClO6, has been solved by powder X-ray diffraction (PXRD). The PXRD pattern of this new phase was recorded at room temperature using synchrotron radiation. The starting structural model was generated by a Monte Carlo simulated annealing method. The final structure was obtained through Rietveld refinement with soft restraints for interatomic bond lengths and angles, except for the aromatic ring, where a rigid-body constraint was applied. The symmetry is orthorhombic (space groupP212121) and the asymmetric unit contains two molecules.

scholarly journals Structure determination of riboflavin by synchrotron high-resolution powder X-ray diffraction

2021 ◽  
Vol 77 (12) ◽  
Author(s):  
Mathieu Guerain ◽  
Frédéric Affouard ◽  
Charline Henaff ◽  
Catherine Dejoie ◽  
Florence Danède ◽  
...  
Keyword(s):  
High Resolution ◽  
Structural Model ◽  
European Synchrotron Radiation Facility ◽  
Stable Form ◽  
X Ray Diffraction ◽  
Pxrd Pattern ◽  
X Ray ◽  
Monte Carlo Simulated Annealing ◽  
Hydroxy Groups

The crystal structure of the stable form of vitamin B2 or riboflavin (C17H20N4O6) was solved using high-resolution powder X-ray diffraction (PXRD). The high-resolution PXRD pattern of riboflavin was recorded at room temperature at the European Synchrotron Radiation Facility (Grenoble, France). The starting structural model was generated using a Monte Carlo simulated annealing method. The final structure was obtained through Rietveld refinement. The positions of the H atoms belonging to hydroxy groups were estimated from computational energy minimizations. The symmetry is orthorhombic with the space group P212121 and the following lattice parameters: a = 20.01308, b = 15.07337 and c = 5.31565 Å.

X-ray powder diffraction structural characterization of Pb1 − x Ba x Zr0.65Ti0.35O3 ceramic

2007 ◽  
Vol 63 (5) ◽  
pp. 713-718 ◽  
Author(s):  
M. Mir ◽  
V. R. Mastelaro ◽  
P. P. Neves ◽  
A. C. Doriguetto ◽  
D. Garcia ◽  
...  
Keyword(s):  
Phase Transition ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Ceramic Materials ◽  
Powder Diffraction Data ◽  
Rietveld Refinements ◽  
X Ray ◽  
Cubic Structure ◽  
Good Agreement

The structure of Pb1 − x Ba x Zr0.65Ti0.35O3 (PBZT) ceramic materials with 0.00 ≤ x ≤ 0.40 was studied using synchrotron X-ray powder diffraction data. According to the Rietveld refinements, the structure of PBZT ceramics with x = 0.00, 0.10 and 0.20 at room temperature was rhombohedral R3c. A phase transition from rhombohedral to cubic was observed at 543 and 463 K for x = 0.10 and 0.20, respectively. The refinement for the compositions x = 0.30 and x = 0.40 showed a cubic structure from 10 to 450 K, in good agreement with the dielectric properties of these samples.

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