scholarly journals Hydrogen bonds in crystalline D-alanine: diffraction and spectroscopic evidence for differences between enantiomers

IUCrJ ◽  
2018 ◽  
Vol 5 (1) ◽  
pp. 6-12 ◽  
Author(s):  
Ezequiel A. Belo ◽  
Jose E. M. Pereira ◽  
Paulo T. C. Freire ◽  
Dimitri N. Argyriou ◽  
Juergen Eckert ◽  
...  
Keyword(s):  
Amino Acids ◽  
Solid State ◽  
Hydrogen Bonds ◽  
Raman Scattering ◽  
Powder Diffraction ◽  
Spectroscopic Studies ◽  
Neutron Powder Diffraction ◽  
Vibrational Modes ◽  
Polarized Raman ◽  
Shed Light

Enantiomeric amino acids have specific physiological functions in complex biological systems. Systematic studies focusing on the solid-state properties of D-amino acids are, however, still limited. To shed light on this field, structural and spectroscopic studies of D-alanine using neutron powder diffraction, polarized Raman scattering and ab initio calculations of harmonic vibrational frequencies were carried out. Clear changes in the number of vibrational modes are observed as a function of temperature, which can be directly connected to variations of the N—D bond lengths. These results reveal dissimilarities in the structural properties of D-alanine compared with L-alanine.

Structure determination of Ba5AlF13 by coupling electron, synchrotron and neutron powder diffraction, solid-state NMR and ab initio calculations

2016 ◽  
Vol 45 (39) ◽  
pp. 15565-15574 ◽  
Author(s):  
Charlotte Martineau ◽  
Mathieu Allix ◽  
Matthew R. Suchomel ◽  
Florence Porcher ◽  
François Vivet ◽  
...  
Keyword(s):  
Solid State ◽  
Dft Calculations ◽  
Powder Diffraction ◽  
Solid State Nmr ◽  
Neutron Powder Diffraction ◽  
Complementary Information ◽  
Electron Synchrotron ◽  
Structure And Dynamics ◽  
Fast Mas

The structure and dynamics of Ba5AlF13 are resolved by combining complementary information from powder diffraction, 27Al and 19F ultra-fast MAS NMR and DFT calculations.

The crystal structure of perdeuterated methanol monoammoniate (CD3OD·ND3) determined from neutron powder diffraction data at 4.2 and 180 K

2009 ◽  
Vol 42 (6) ◽  
pp. 1054-1061 ◽  
Author(s):  
A. D. Fortes ◽  
I. G. Wood ◽  
K. S. Knight
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Neutron Powder Diffraction ◽  
Relative Volume ◽  
Powder Diffraction Data ◽  
Orthorhombic Space Group ◽  
Neutron Powder Diffraction Data

The crystal structure of perdeuterated methanol monoammoniate, CD3OD·ND3, has been solved from neutron powder diffraction data collected at 4.2 and 180 K. The crystal structure is orthorhombic, space groupPbca(Z= 8), with unit-cell dimensionsa= 11.02320 (7),b= 7.66074 (6),c= 7.59129 (6) Å,V= 641.053 (5) Å3[ρcalc= 1162.782 (9) kg m−3] at 4.2 K, anda= 11.21169 (5),b= 7.74663 (4),c= 7.68077 (5) Å,V= 667.097 (4) Å3[ρcalc= 1117.386 (7) kg m−3] at 180 K. The crystal structure was determined byab initiomethods from the powder data; atomic coordinates and anisotropic displacement parameters were subsequently refined by the Rietveld method toRp< 3% at both temperatures. The crystal comprises a sheet-like structure in thebccrystallographic plane, consisting of strongly hydrogen bonded elements; these sheets are stacked along theaaxis, and adjacent sheets are linked by what may be comparatively weak C—D...O hydrogen bonds. Within the strongly bonded sheet structure, ND3molecules are tetrahedrally coordinated by the hydroxy moieties of the methanol molecule, accepting one hydrogen bond (O—D...N) of length ∼1.75 Å, and donating three hydrogen bonds (N—D...O) of length 2.15–2.25 Å. Two of the methyl deuterons appear to participate in weak interlayer hydrogen bonds (C—D...O) of length 2.7–2.8 Å. The hydrogen bonds are ordered at both 4.2 and 180 K. The relative volume change on warming from 4.2 to 180 K, ΔV/V, is +4.06%, which is comparable to, but more nearly isotropic (as determined from the relative change in axial lengths,e.g.Δa/a) than, that observed in deuterated methanol monohydrate.

scholarly journals The crystal chemistry and electrical properties of Fe doped Ca12Al14O33 (Mayenite)

2021 ◽  
Vol 40 (4) ◽  
pp. 591-597
Author(s):  
S.N. Ude ◽  
C.J. Rawn ◽  
T.T. Meek
Keyword(s):  
Solid State ◽  
Electrical Properties ◽  
Crystal Chemistry ◽  
Powder Diffraction ◽  
Synthesis Method ◽  
Neutron Powder Diffraction ◽  
Solid State Synthesis ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Phase Pure

X-ray and neutron powder diffraction have been used to study the crystal chemistry of Fe doped mayenite (Ca12Al14-xFexO33). Solid- state synthesis was used to prepare Ca12Al14-xFexO33 where x = 0, 0.1, 0.2, 0.5 and 0.6 and the citrate gel route was used to prepare Ca12Al14-xFexO33 where x = 0, 0.05, 0.1, 0.2, 0.3 and 0.4. X-ray powder diffraction data indicate that samples with the same composition but synthesized by the citrate gel route were more likely to be phase pure than samples obtained by traditional solid-state synthesis. The refined lattice parameters were observed to increase with increasing Fe concentration, irrespective of the synthesis method. Refined neutron powder data confirm that Fe is going into Al site rather than Ca site. A 2-point probe was used to measure the electrical properties of the Fe doped citrate gel synthesized samples and showed that the resistivity increases for the Fe doped samples compared to the undoped mayenite.

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