Partial pair distribution functions in icosahedral Al-Mn studied by contrast variation in neutron diffraction

1987 ◽  
Vol 48 (11) ◽  
pp. 1981-1989 ◽  
Author(s):  
J.-M. Dubois ◽  
Ch. Janot
Keyword(s):  
Neutron Diffraction ◽  
Distribution Functions ◽  
Contrast Variation ◽  
Pair Distribution Functions

Structure of Amorphous(Co,Mn)76B24-and (Co,Mn)85B15-Alloys by Means of X-Ray- and Neutron-Diffraction

1989 ◽  
Vol 44 (6) ◽  
pp. 495-503 ◽  
Author(s):  
M. Heckele ◽  
P. Lamparter ◽  
S. Steeb ◽  
R. Bellissent
Keyword(s):  
Neutron Diffraction ◽  
Short Range ◽  
Melt Spinning ◽  
Measured Data ◽  
Distribution Functions ◽  
Manganese Concentration ◽  
Intensity Pattern ◽  
X Ray ◽  
Large Intensity ◽  
Pair Distribution Functions

Amorphous (Co1-xMnx)85B15- (x = 0.07; 0.22; 0.39) and (Co1-xMnx)76B24- (x = 0; 0.07; 0.22) alloys were produced by melt-spinning and investigated by X-ray- and neutron-diffraction. The variation of x, i.e. the manganese concentration did not influence the X-ray intensity pattern, which suggests that no larger topological changes in the structure took place. However, using neutrons, the variation of x caused large intensity variations. These lead for large x to negative values in the total pair distribution functions g(R). From this behaviour it is concluded that cobalt and manganese cannot be mutually substituted but form a chemical short range order with preference for Co-Mn-pairs compared to Mn-Mn- and Co-Co-pairs. The metal-boron-correlations are preferentially cobalt-boron-correlations. The evaluation of measured data yielded no direct boron-boron-contacts.

scholarly journals NXFit: a program for simultaneously fitting X-ray and neutron diffraction pair-distribution functions to provide optimized structural parameters

2014 ◽  
Vol 47 (5) ◽  
pp. 1790-1796 ◽  
Author(s):  
David Pickup ◽  
Robert Moss ◽  
Robert Newport
Keyword(s):  
Neutron Diffraction ◽  
Amorphous Materials ◽  
Structural Parameters ◽  
Sol Gel ◽  
Distribution Functions ◽  
X Ray ◽  
Atomic Correlation ◽  
Neutron Pair ◽  
Derived Data ◽  
Pair Distribution Functions

NXFitis a program for obtaining optimized structural parameters from amorphous materials by simultaneously fitting X-ray and neutron pair-distribution functions. Partial correlation functions are generated inQspace, summed and Fourier transformed for comparison with the experimental data inrspace.NXFituses the Nelder–Mead method to vary a set of `best guess' parameters to achieve a fit to experimentally derived data. The output parameters fromNXFitare coordination number, atomic separation and disorder parameter for each atomic correlation used in the fitting process. The use ofNXFithas been demonstrated by fitting both X-ray and neutron diffraction data from two quite different amorphous materials: a melt-quenched (Na2O)0.5(P2O5)0.5glass and a (TiO2)0.18(SiO2)0.82sol–gel.

Atom Pair Distribution Functions of Liquid Water at 25 C from Neutron Diffraction

Science ◽  
1982 ◽  
Vol 217 (4564) ◽  
pp. 1033-1034 ◽  
Author(s):  
A. H. NARTEN ◽  
W. E. THIESSEN ◽  
L. BLUM
Keyword(s):  
Neutron Diffraction ◽  
Liquid Water ◽  
Distribution Functions ◽  
Atom Pair ◽  
Pair Distribution Functions

Neutron diffraction, inelastic scattering and the structure of amphiphiles and macromolecules in solution

1975 ◽  
Vol 345 (1640) ◽  
pp. 119-144 ◽  
Keyword(s):  
Neutron Diffraction ◽  
Inelastic Scattering ◽  
Cross Sections ◽  
Biological Molecules ◽  
Variation Method ◽  
Contrast Variation ◽  
Structure And Dynamics ◽  
Spin Resonance ◽  
Scattering Lengths ◽  
Scattering Cross Sections

The methods by which neutron diffraction and inelastic scattering may be used to study the structure and dynamics of solutions are reviewed, with particular reference to solutions of amphiphile and biological molecules in water. Neutron methods have particular power because the scattering lengths for protons and deuterons are of opposite sign, and hence there exists the possibility of obtaining variable contrast between the scattering of the aqueous medium and the molecules in it. In addition, the contrast variation method is also applicable to inelastic scattering studies whereby the dynamics of one component of the solution can be preferentially studied due to large and variable differences in the scattering cross sections. Both applications of contrast variation are illustrated with examples of amphiphile-water lamellar mesophases, diffraction from collagen, viruses, and polymer solutions. Inelastic scattering observations and the dynamics of water between the lamellar sheets allow microscopic measurements of the water diffusion along and perpendicular to the layers. The information obtained is complementary to that from nuclear magnetic resonance and electron spin resonance studies of diffusion.

scholarly journals Local structure and distortions of mixed methane-carbon dioxide hydrates

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Bernadette R. Cladek ◽  
S. Michelle Everett ◽  
Marshall T. McDonnell ◽  
Matthew G. Tucker ◽  
David J. Keffer ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Exchange Process ◽  
Carbon Dioxide Sequestration ◽  
Distribution Functions ◽  
Atomic Scale ◽  
Mixed Gas ◽  
Pure Compounds ◽  
Dynamics Simulations ◽  
Pair Distribution Functions ◽  
Methane Carbon

AbstractA vast source of methane is found in gas hydrate deposits, which form naturally dispersed throughout ocean sediments and arctic permafrost. Methane may be obtained from hydrates by exchange with hydrocarbon byproduct carbon dioxide. It is imperative for the development of safe methane extraction and carbon dioxide sequestration to understand how methane and carbon dioxide co-occupy the same hydrate structure. Pair distribution functions (PDFs) provide atomic-scale structural insight into intermolecular interactions in methane and carbon dioxide hydrates. We present experimental neutron PDFs of methane, carbon dioxide and mixed methane-carbon dioxide hydrates at 10 K analyzed with complementing classical molecular dynamics simulations and Reverse Monte Carlo fitting. Mixed hydrate, which forms during the exchange process, is more locally disordered than methane or carbon dioxide hydrates. The behavior of mixed gas species cannot be interpolated from properties of pure compounds, and PDF measurements provide important understanding of how the guest composition impacts overall order in the hydrate structure.

Molecular dynamics study of the hydrophobic 6,6-ionene oligocation in aqueous solution with sodium halides

2010 ◽  
Vol 82 (10) ◽  
pp. 1943-1955 ◽  
Author(s):  
Maksym Druchok ◽  
Vojko Vlachy
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Distribution Functions ◽  
Low Molecular Weight ◽  
Specific Effects ◽  
Sodium Cations ◽  
Counter Ions ◽  
Sodium Halides ◽  
Explicit Water ◽  
Pair Distribution Functions

An explicit water molecular dynamics (MD) simulation is presented of a solution modeling aliphatic 6,6-ionene oligocations mixed with low-molecular-weight electrolytes. In all cases, the co-ions were sodium cations and the counterions were fluoride, chloride, bromide, or iodide anions. The simple point charge/extended (SPC/E) model was used to describe water. The results of the simulation at T = 278 K (the data for 298 K were obtained earlier) and T = 318 K are presented in the form of pair distributions between various atoms and/or between ions in the system. We were interested in how temperature variation modifies the ion-specific effects, revealed by the various pair distribution functions (PDFs). The results were compared with previous calculations for the less hydrophobic 3,3-ionene solutions. Simulations of 6,6-ionene solutions containing mixtures of fluoride and iodide counter-ions at T = 298 K were also presented.

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