Model-independent method for reconstruction of scattering-length-density profiles using neutron or x-ray reflectivity data

1993 ◽  
Vol 47 (5) ◽  
pp. 3174-3190 ◽  
Author(s):  
Xiao-Lin Zhou ◽  
Sow-Hsin Chen
Keyword(s):  
Scattering Length ◽  
Independent Method ◽  
Density Profiles ◽  
X Ray ◽  
Scattering Length Density ◽  
Model Independent ◽  
Reflectivity Data

Model-independent determination of the surface scattering-length-density profile from specular reflectivity data

1992 ◽  
Vol 25 (2) ◽  
pp. 129-145 ◽  
Author(s):  
J. S. Pedersen
Keyword(s):  
Density Profile ◽  
Fourier Transformation ◽  
Scattering Length ◽  
Simulated Data ◽  
Limited Range ◽  
Square Root ◽  
Scattering Length Density ◽  
Angle Scattering ◽  
Specular Reflectivity ◽  
Reflectivity Data

An approach for analysing neutron and X-ray specular reflectivity data from stratified media having variation in the scattering-length density near the surface is described. The method has its origin in small-angle scattering and it is composed of two steps: (i) indirect Fourier transformation [Glatter (1977). J. Appl. Cryst. 10, 415–421] giving the profile correlation function p(z) of the derivative dρ/dz of the scattering-length density; (ii) square-root deconvolution [Glatter (1981). J. Appl. Cryst. 14, 101–108] giving dρ/dz and ρ, the scattering-length-density profile. The only requirement for applying the method is that the scattering-length density varies only in a limited range. In nearly all cases the approach does not require any knowledge of the chemical composition of the surface layer and consequently incorporates a certain degree of objectivity. The method gives the smoothest profile which agrees with the experimental reflectivity data. The method is tested on simulated reflectivity data for a series of different surface profiles and subsequently used for analysing experimental data on fluorocarbon amphiphiles in water and salt solutions. The tests on simulated data show that the indirect Fourier transformation gives correlation functions agreeing very well with the corresponding functions of the original profiles. It is further demonstrated that the square-root deconvolution gives reliable results for the scattering-length-density profiles.

A model independent method to deconvolve hard X-ray spectra

1984 ◽  
Vol 224 (1-2) ◽  
pp. 298-302 ◽  
Author(s):  
V.F. Polcaro ◽  
A. Bazzano ◽  
P. Ubertini ◽  
C. La Padula ◽  
R.K. Manchanda
Keyword(s):  
Independent Method ◽  
X Ray ◽  
Model Independent

Model-independent inversion of x-ray or neutron reflectivity data

2001 ◽  
Vol 63 (19) ◽  
Author(s):  
Erman Bengu ◽  
Monica Salud ◽  
L. D. Marks
Keyword(s):  
Neutron Reflectivity ◽  
X Ray ◽  
Model Independent ◽  
Reflectivity Data

String Fit: a new structurally oriented X-ray and neutron reflectivity evaluation technique

2001 ◽  
Vol 34 (3) ◽  
pp. 239-251 ◽  
Author(s):  
Erich Politsch
Keyword(s):  
Density Profile ◽  
Ad Hoc ◽  
Structural Characteristics ◽  
Scattering Length ◽  
Radius Of Gyration ◽  
Data Sets ◽  
Molecular Conformations ◽  
X Ray ◽  
Scattering Length Density ◽  
Molecular Arrangement

A novel method for the analysis of neutron and X-ray reflectivity measurements is presented. In contrast to existing methods, the new data fitting approach is structurally oriented and therefore only requires information about the chemical structure of studied molecules and no otherad hocassumptions. Apart from the inversion of reflectivity into scattering length density profile, the inversion of scattering length density profile into molecular arrangement is addressed systematically for non-trivial molecular conformations for the first time. This includes the calculation of structural characteristics, such as radius of gyration or chain order parameters, based on measured reflectograms. Another important option is the possibility to evaluate simultaneously neutron and X-ray reflectograms of a given sample. For better convergence, especially for complex simultaneous evaluations, an effective extension of the normally used least-squares deviation function is introduced. Different simulated molecular ensembles are used to illustrate the features of the new approach; typically, excellent agreement between the simulated starting and final deduced data sets is achieved.

scholarly journals Mutually Beneficial Combination of Molecular Dynamics Computer Simulations and Scattering Experiments

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 507
Author(s):  
Nebojša Zec ◽  
Gaetano Mangiapia ◽  
Alex C. Hendry ◽  
Robert Barker ◽  
Alexandros Koutsioubas ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Scattering Length ◽  
Md Simulations ◽  
Real Space ◽  
Scattering Data ◽  
Phospholipid Membrane ◽  
Density Profiles ◽  
X Ray ◽  
Angle Scattering ◽  
Scattering Measurements

We showcase the combination of experimental neutron scattering data and molecular dynamics (MD) simulations for exemplary phospholipid membrane systems. Neutron and X-ray reflectometry and small-angle scattering measurements are determined by the scattering length density profile in real space, but it is not usually possible to retrieve this profile unambiguously from the data alone. MD simulations predict these density profiles, but they require experimental control. Both issues can be addressed simultaneously by cross-validating scattering data and MD results. The strengths and weaknesses of each technique are discussed in detail with the aim of optimizing the opportunities provided by this combination.

scholarly journals Carbonaceous Materials Investigated by Small-Angle X-ray and Neutron Scattering

2020 ◽  
Vol 6 (4) ◽  
pp. 82
Author(s):  
Eneli Härk ◽  
Matthias Ballauff
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Carbon Nanomaterials ◽  
Scattering Length ◽  
Carbonaceous Materials ◽  
X Ray ◽  
Scattering Length Density ◽  
X Ray Scattering ◽  
Ray Scattering

Carbonaceous nanomaterials have become important materials with widespread applications in battery systems and supercapacitors. The application of these materials requires precise knowledge of their nanostructure. In particular, the porosity of the materials together with the shape of the pores and the total internal surface must be known accurately. Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) present the methods of choice for this purpose. Here we review our recent investigations using SAXS and SANS. We first describe the theoretical basis of the analysis of carbonaceous material by small-angle scattering. The evaluation of the small-angle data relies on the powerful concept of the chord length distribution (CLD) which we explain in detail. As an example of such an evaluation, we use recent analysis by SAXS of carbide-derived carbons. Moreover, we present our SAXS analysis on commercially produced activated carbons (ACN, RP-20) and provide a comparison with small-angle neutron scattering data. This comparison demonstrates the wealth of additional information that would not be obtained by the application of either method alone. SANS allows us to change the contrast, and we summarize the main results using different contrast matching agents. The pores of the carbon nanomaterials can be filled gradually by deuterated p-xylene, which leads to a precise analysis of the pore size distribution. The X-ray scattering length density of carbon can be matched by the scattering length density of sulfur, which allows us to see the gradual filling of the nanopores by sulfur in a melt-impregnation procedure. This process is important for the application of carbonaceous materials as cathodes in lithium/sulfur batteries. All studies summarized in this review underscore the great power and precision with which carbon nanomaterials can be analyzed by SAXS and SANS.

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