scholarly journals In situ structural and texture analyses of monoclinic phase for polycrystalline Ni-rich Ti49.86Ni50.14 alloy from neutron diffraction data

2008 ◽  
Vol 23 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Husin Sitepu
Keyword(s):  
Phase Transformation ◽  
Neutron Diffraction ◽  
Differential Scanning Calorimeter ◽  
Diffraction Data ◽  
Monoclinic Phase ◽  
Neutron Diffraction Data ◽  
Monoclinic Crystal ◽  
Data Set ◽  
One Step

Phase transformation temperatures of a polycrystalline Ni-rich Ti49.86Ni50.14 shape memory alloy were investigated using a differential scanning calorimeter. In situ structural and texture analyses of the monoclinic Ti49.86Ni50.14 were investigated using neutron powder diffractometer technique. Differential scanning calorimeter results showed that this Ni-rich alloy has a one-step cubic to monoclinic martensitic phase transformation on cooling and a one-step monoclinic to cubic transformation on heating. In situ high-resolution neutron powder diffraction data of the monoclinic phase from low temperatures to room temperature on heating are consistent with the differential scanning calorimeter’s heating results. In addition, the refined monoclinic crystal structure parameters for all neutron diffraction data sets agree satisfactorily with single-crystal X-ray diffraction results. The multiple-data-set capabilities of the GSAS Rietveld refinement program, with a generalized spherical-harmonics description was used successfully to extract the texture description directly from a simultaneous refinement using 52 time-of-flight monoclinic neutron diffraction patterns, taken from a polycrystalline sample held in 13 orientations inside the diffractometer.

Design of a novel Peltier-based cooling device and its use in neutron diffraction data collection of perdeuterated yeast pyrophosphatase

2010 ◽  
Vol 43 (5) ◽  
pp. 1113-1120 ◽  
Author(s):  
Esko Oksanen ◽  
François Dauvergne ◽  
Adrian Goldman ◽  
Monika Budayova-Spano
Keyword(s):  
Data Collection ◽  
Neutron Diffraction ◽  
Diffraction Data ◽  
Catalytic Mechanism ◽  
Inorganic Pyrophosphatase ◽  
Neutron Diffraction Data ◽  
Cooling Device ◽  
Data Set ◽  
X Ray ◽  
X Ray Crystallography

H atoms play a central role in enzymatic mechanisms, but H-atom positions cannot generally be determined by X-ray crystallography. Neutron crystallography, on the other hand, can be used to determine H-atom positions but it is experimentally very challenging. Yeast inorganic pyrophosphatase (PPase) is an essential enzyme that has been studied extensively by X-ray crystallography, yet the details of the catalytic mechanism remain incompletely understood. The temperature instability of PPase crystals has in the past prevented the collection of a neutron diffraction data set. This paper reports how the crystal growth has been optimized in temperature-controlled conditions. To stabilize the crystals during neutron data collection a Peltier cooling device that minimizes the temperature gradient along the capillary has been developed. This device allowed the collection of a full neutron diffraction data set.

Preliminary results of neutron and X-ray diffraction data collection on a lytic polysaccharide monooxygenase under reduced and acidic conditions

2021 ◽  
Vol 77 (4) ◽  
Author(s):  
Gabriela C. Schröder ◽  
William B. O'Dell ◽  
Paul D. Swartz ◽  
Flora Meilleur
Keyword(s):  
Reaction Mechanism ◽  
Neutron Diffraction ◽  
Diffraction Data ◽  
Crystalline Cellulose ◽  
Neutron Diffraction Data ◽  
Lytic Polysaccharide Monooxygenase ◽  
Nondestructive Technique ◽  
Data Set ◽  
Polysaccharide Monooxygenases ◽  
Acidic Conditions

Lytic polysaccharide monooxygenases (LPMOs) are copper-center enzymes that are involved in the oxidative cleavage of the glycosidic bond in crystalline cellulose and other polysaccharides. The LPMO reaction is initiated by the addition of a reductant and oxygen to ultimately form an unknown activated copper–oxygen species that is responsible for polysaccharide-substrate H-atom abstraction. Given the sensitivity of metalloproteins to radiation damage, neutron protein crystallography provides a nondestructive technique for structural characterization while also informing on the positions of H atoms. Neutron cryo-crystallography permits the trapping of catalytic intermediates, thereby providing insight into the protonation states and chemical nature of otherwise short-lived species in the reaction mechanism. To characterize the reaction-mechanism intermediates of LPMO9D from Neurospora crassa, a cryo-neutron diffraction data set was collected from an ascorbate-reduced crystal. A second neutron diffraction data set was collected at room temperature from an LPMO9D crystal exposed to low-pH conditions to probe the protonation states of ionizable groups involved in catalysis under acidic conditions.

Rapid structure determination of the hydrogen-containing compound Cs2C2O4·H2O by joint single-crystal X-ray and powder neutron diffraction

2007 ◽  
Vol 63 (3) ◽  
pp. 426-432 ◽  
Author(s):  
Mark T. Weller ◽  
Paul F. Henry ◽  
Mark E. Light
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Structure Determination ◽  
Neutron Diffraction Data ◽  
Data Set ◽  
X Ray ◽  
Neutron Diffractometer ◽  
Powder Neutron Diffraction

The structure determination of caesium oxalate monohydrate using single-crystal X-ray diffraction, powder neutron diffraction data and a combination of both has been undertaken. Results show that even for hydrogen-containing materials data collected rapidly on a high-flux neutron diffractometer improve the refinement such that accurate positional and thermal displacement parameters can be extracted for all atom types. This contrasts with structural models extracted from either data set alone that demonstrate the inherent limitations of the individual diffraction methods. The rapidity with which useful neutron diffraction data has been collected from hydrogen-containing compounds, 10 min in this study, indicates that the technique should be widely applicable allowing the facile and accurate extraction of hydrogen positions for many compounds.

Structural Investigations on Scandium Substituted Nasicons. Order Disorder Effects

1988 ◽  
Vol 135 ◽  
Author(s):  
A. Clearfield ◽  
P.G. Hinson ◽  
P.R. Rudolf ◽  
P.J. Squattrito
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Monoclinic Phase ◽  
Similar Type ◽  
Sodium Ions ◽  
Neutron Diffraction Data ◽  
Structural Investigations ◽  
Disorder Effects ◽  
Phosphate Compound ◽  
Phosphate Groups

AbstractNeutron diffraction data were used to refine the structures of three scandium substituted NASICONS: Na2 ZrSc(PO4)3, R3c Na2.5 Zr1.8 Sc0.2 Si1.7 O12 R3c and Na2.7. Zr1.0 Sc0.2Si1.5 P1.5O12, C2/c. The phosphate (compound 1) exhibited oxygen disorder. The second compound exhibited a similar type of oxygen disorder but also an interstitial Na+ position. The oxygen disorder in compound 2 apparently results from the position of the interstitial Nae whereas it is suggested that the Sc site in Na2 ZrSC(PO4)3 is slightly removed from that of the Zr position, requiring a shift of phosphate groups. In contrast the monoclinic phase does not exhibit oxygen disorder and all the sodium ions reside within the cavities.

In situ X-ray and neutron powder diffraction study of LaNi5-x Snx–H systems

2004 ◽  
Vol 837 ◽  
Author(s):  
Yumiko Nakamura ◽  
Robert C. Bowman ◽  
Etsuo Akiba
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Lattice Strain ◽  
Profile Analysis ◽  
Lattice Parameter ◽  
Hydride Phase ◽  
Neutron Diffraction Data ◽  
X Ray ◽  
Hydrogen Deuterium

ABSTRACTWe have studied structural change and lattice strain formation during absorption and desorption of hydrogen (deuterium) by high purity LaNi5-x Snx alloys (x = 0.22, 0.25) using in situ X-ray and neutron diffraction along with simultaneously measuring the P-C isotherms. From profile analysis of the X-ray diffraction data, lattice parameter and lattice strain in each hydriding state are evaluated. In situ neutron diffraction data provided hydrogen occupation changing with hydrogen content. Significant lattice contract and strain formation were observed in the hydride phase in desorption. This behavior was related with decrease in hydrogen occupation in the hydride phase revealed from the neutron diffraction data.

In Situ Neutron Diffraction Studies of the Pseudoelastic-Like Behaviour of Hydrostatically Extruded Mg-Al-Zn Alloy

2008 ◽  
Vol 571-572 ◽  
pp. 107-112 ◽  
Author(s):  
Ondrej Muránsky ◽  
David G. Carr ◽  
Petr Šittner ◽  
E.C. Oliver ◽  
P. Dobroň
Keyword(s):  
Magnesium Alloy ◽  
Neutron Diffraction ◽  
Diffraction Data ◽  
Driving Force ◽  
Extrusion Direction ◽  
Neutron Diffraction Data ◽  
Tensile Stresses ◽  
In Situ Neutron Diffraction ◽  
Zn Alloy

In-situ neutron diffraction has been used to study the pseudoelastic-like behaviour of hydrostatically extruded AZ31 magnesium alloy during stress-strain cycles in compression and tension along the extrusion direction. It has been confirmed that the activation of reversal twinning processes during unloading is responsible for the macroscopically observed hysteresis effect. Moreover, neutron diffraction data reveals the existence of high tensile stresses in grains which have just experienced significant twinning activity prior to the start of the unload cycle. It is thus proposed that this tensile stresses provides the necessary driving force for the activation of untwinning in already twinned grains.

A neutron-diffraction study of potassium bromide

1973 ◽  
Vol 137 (4) ◽  
Author(s):  
G. E. Bacon ◽  
D. H. Titterton ◽  
C. R. Walker
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Diffuse Scattering ◽  
Scattering Amplitude ◽  
Coherent Scattering ◽  
Neutron Diffraction Study ◽  
Potassium Bromide ◽  
Neutron Diffraction Data ◽  
Thermal Diffuse Scattering ◽  
Thermal Diffuse

AbstractNeutron-diffraction data have been collected from a KBr single crystal. 380 reflections were measured, reducing to 23 when averaged over equivalents. Data were corrected for extinction and thermal diffuse scattering and refinement yielded a neutron coherent scattering amplitude

Extracting fluid structures from neutron diffraction data

1995 ◽  
Vol 236 (1-2) ◽  
pp. 1-7 ◽  
Author(s):  
Haluk Resat ◽  
Enci Zhong ◽  
Harold L. Friedman
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Neutron Diffraction Data
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