Relationships between the medium-range structure of glasses and crystals

2000 ◽  
Vol 64 (3) ◽  
pp. 425-434 ◽  
Author(s):  
P. H. Gaskell
Keyword(s):  
Chalcogenide Glasses ◽  
Local Environment ◽  
Quantitative Agreement ◽  
Real Space ◽  
Scattering Data ◽  
Bragg Scattering ◽  
Structure Of Glasses ◽  
Medium Range ◽  
Unknown Structure ◽  
Space Data

AbstractThe known structure of a crystalline phase is almost always useful in investigating the unknown structure of the compositionally equivalent glass. For the local environment around elements like Si, B and P, the correspondence between site geometry and symmetry can be impressively close. Beyond near neighbours, any relationship becomes less obvious – at least in real-space data. Progress in understanding the medium-range structures of glasses has been painfully slow as a result. One essential clue is given by reciprocal-space features at low Q (scattering vector) in X-ray or neutron scattering data, which are clearly related to the medium-range structure. Interpretation of these features as ‘quasi-Bragg’ scattering allows direct comparison between the structures of the glass and equivalent crystalline phases. Applications of this method will be illustrated in borates and silicates, together with some chalcogenide glasses. Correspondence between low-Q features for these glasses and compositionally-equivalent crystals is qualitatively good. In some cases there is semi-quantitative agreement too. Thus the essential flavour of the medium-range structure of several typical glasses appears to be interpretable, rather easily.

Mitigation of errors in pair distribution function analysis of nanoparticles

2011 ◽  
Vol 44 (4) ◽  
pp. 788-797 ◽  
Author(s):  
Katharine Mullen ◽  
Igor Levin
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Function Analysis ◽  
Structural Parameters ◽  
Real Space ◽  
Scattering Data ◽  
Parameter Estimates ◽  
Total Scattering ◽  
Counting Statistics ◽  
Space Data

Information on the size and structure of nanoparticles can be obtainedviaanalysis of the atomic pair distribution function (PDF), which is calculated as the Fourier transform of X-ray/neutron total scattering. The structural parameters are commonly extracted by fitting a model PDF calculated from atomic coordinates to the experimental data. This paper discusses procedures for minimizing systematic errors in PDF calculations for nanoparticles and also considers the effects of noise due to counting statistics in total scattering data used to obtain the PDF. The results presented here demonstrate that smoothing of statistical noise in reciprocal-space data can improve the precision of parameter estimates obtained from PDF analysis, facilitating identification of the correct model (from multiple plausible choices) from real-space PDF fits.

scholarly journals Structure of the amorphous titania precursor phase of N-doped photocatalysts

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8619-8627
Author(s):  
I. E. Grey ◽  
P. Bordet ◽  
N. C. Wilson
Keyword(s):  
Thermal Analyses ◽  
Real Space ◽  
Ammonia Solution ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Amorphous Titania ◽  
Precursor Phase ◽  
Titania Precursor ◽  
Titanyl Sulphate

Amorphous titania samples prepared by ammonia solution neutralization of titanyl sulphate have been characterized by chemical and thermal analyses, and with reciprocal-space and real-space fitting of wide-angle synchrotron X-ray scattering data.

Autocorrelation function of the spin misalignment in magnetic small-angle neutron scattering: application to nanocrystalline metals

2013 ◽  
Vol 46 (3) ◽  
pp. 788-790 ◽  
Author(s):  
Andreas Michels ◽  
Jens-Peter Bick
Keyword(s):  
Neutron Scattering ◽  
Autocorrelation Function ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Anisotropy Field ◽  
Real Space ◽  
Scattering Data ◽  
Stiffness Constant ◽  
The Mean ◽  
Cobalt And Nickel

Real-space magnetic small-angle neutron scattering data from nanocrystalline cobalt and nickel have been analysed in terms of a recently developed micromagnetic theory for the autocorrelation function of the spin misalignment [Michels (2010).Phys. Rev. B,82, 024433]. The approach provides information on the exchange-stiffness constant and on the mean magnetic `anisotropy-field' radius.

The Event Search Engine

2012 ◽  
pp. 70-82
Author(s):  
Takeshi Okadome ◽  
Yasue Kishino ◽  
Takuya Maekawa ◽  
Koji Kamei ◽  
Yutaka Yanagisawa ◽  
...  
Keyword(s):  
Search Engine ◽  
Real World ◽  
Local Environment ◽  
Real Space ◽  
Sensor Data ◽  
The Internet ◽  
Web Browser ◽  
Quantity Representation ◽  
Data Segment ◽  
The Web

In a remote or local environment in which a sensor network always collects data produced by sensors attached to physical objects, the engine presented here saves the data sent through the Internet and searches for data segments that correspond to real-world events by using natural language (NL) words in a query that are input in an web browser. The engine translates each query into a physical quantity representation searches for a sensor data segment that satisfies the representation, and sends back the event occurrence time, place, or related objects as a reply to the query to the remote or local environment in which the web browser displays them. The engine, which we expect to be one of the upcoming Internet services, exemplifies the concept of symbiosis that bridges the gaps between the real space and the digital space.

ABS: a program to determine absolute configuration and evaluate anomalous scatterer substructure

2004 ◽  
Vol 37 (3) ◽  
pp. 498-499 ◽  
Author(s):  
Quan Hao
Keyword(s):  
Absolute Configuration ◽  
Protein Structures ◽  
Real Space ◽  
Scattering Data ◽  
Anomalous Scattering ◽  
Acta Cryst ◽  
Mad Phasing ◽  
Unknown Protein ◽  
Multi Wavelength ◽  
The Absolute

In single- or multi-wavelength anomalous dispersion (SAD/MAD) phasing, one of the essential steps is to find the absolute configuration (hand) of the anomalous scatterers. A computer program,ABS, based on an algorithm proposed by Woolfson & Yao [Acta Cryst. (1994), D50, 7–10] has been written to determine the absolute configuration by using anomalous scattering data. It also calculates a real-space figure of merit (FOM) that can be used to assess the quality of the solution for anomalous scatterer sites. TheABSprogram has been successfully applied in severalab initiophasing cases, including some previously unknown protein structures. The program is included in theCCP4suite.

Analysis of diffuse scattering from the mineral mullite

1994 ◽  
Vol 27 (5) ◽  
pp. 742-754 ◽  
Author(s):  
B. D. Butler ◽  
T. R. Welberry
Keyword(s):  
Diffuse Scattering ◽  
Real Space ◽  
Order Parameters ◽  
Scattering Data ◽  
Local Order ◽  
Near Neighbour ◽  
Diffuse Intensity ◽  
Space Model ◽  
Least Squares Techniques ◽  
Space Volume

A full reciprocal-space volume of diffuse scattering data from a single-crystal of the mineral mullite, Al2(Al2 + 2x Si2 − 2x )O10 − x , x = 0.4, was collected. These data were analysed using least-squares techniques by writing an equation for the diffuse scattering that involves only the local order between vacancies on specific oxygen sites in the material. The effect of the large, but predictable, cation shifts on the diffuse intensity is taken account of in the coefficients of the oxygen-vacancy short-range-order intensities. This analysis shows that the vacancies are negatively correlated at the near-neighbour ½ 〈110〉, [110], 〈001〉 and 〈011〉 interatomic vectors and positively correlated along the 〈010〉, 〈101〉, ½ 〈112〉 and ½ 〈310〉 vectors. Subsequent Monte Carlo modelling of the structure based on these local-order parameters demonstrates that the structure of mullite is dominated by effective near-neighbour vacancy–vacancy repulsive interactions. A real-space model of mullite is presented that is approximately consistent with the measured local-order parameters.

Medium-Range Structure in Chalcogenide Glasses

1998 ◽  
Vol 37 (Part 1, No. 4A) ◽  
pp. 1747-1753 ◽  
Author(s):  
Keiji Tanaka
Keyword(s):  
Chalcogenide Glasses ◽  
Medium Range

Fluctuation X-ray Microscopy for Measuring Medium-Range Order

2004 ◽  
Vol 840 ◽  
Author(s):  
Lixin Fan ◽  
Ian McNulty ◽  
David Paterson ◽  
Michael M.J. Treacy ◽  
J. Murray Gibson
Keyword(s):  
Amorphous Materials ◽  
Structural Changes ◽  
Real Space ◽  
Polystyrene Latex ◽  
Range Order ◽  
Disordered Materials ◽  
X Ray ◽  
Novel Approach ◽  
Wide Range ◽  
Medium Range

ABSTRACTMany x-ray techniques exist to probe long- and short-range order in matter, in real space by imaging and in reciprocal space by diffraction and scattering. However, measuring mediumrange order (MRO) in disordered materials is a long-standing problem. Based on fluctuation electron microscopy, which was applied successfully to the understanding of MRO in amorphous materials, we have developed fluctuation x-ray microscopy (FXM). This novel approach offers quantitative insight into medium-range correlations in materials at nanometer and larger length scales. It examines spatially resolved fluctuations in the intensity of a series of x-ray speckle patterns. The speckle variance depends on higher order correlations that are more sensitive to MRO. Systematically measuring the speckle variance as function of the momentum transfer and x-ray illumination size produces a fluctuation map that contains information about the degree of MRO and the correlation length. This approach can be used for the exploration of MRO and subtle spatial structural changes in a wide range of disordered materials from soft condensed matter to nanowire arrays, semiconductor quantum dot arrays and magnetic materials. It will also help us to understand the mechanisms of order-disorder transitions and may lead to control of ordering, which is important in developing ordered structures tailored for particular applications. A theory for FXM and preliminary experimental results from polystyrene latex spheres are discussed in this paper.

scholarly journals Nonlinear plasmonics at high temperatures

Nanophotonics ◽  
2017 ◽  
Vol 6 (1) ◽  
pp. 317-328 ◽  
Author(s):  
Yonatan Sivan ◽  
Shi-Wei Chu
Keyword(s):  
Physical Mechanism ◽  
Continuous Wave ◽  
Optical Nonlinearity ◽  
Quantitative Agreement ◽  
Visible Spectral Range ◽  
Scattering Data ◽  
Heat Equations ◽  
Nonlinear Scattering ◽  
Nonlinear Plasmonics ◽  
Increasing Temperature

AbstractWe solve the Maxwell and heat equations self-consistently for metal nanoparticles under intense continuous wave (CW) illumination. Unlike previous studies, we rely on experimentally-measured data for metal permittivity for increasing temperature and for the visible spectral range. We show that the thermal nonlinearity of the metal can lead to substantial deviations from the predictions of the linear model for the temperature and field distribution and, thus, can explain qualitatively the strong nonlinear scattering from such configurations observed experimentally. We also show that the incompleteness of existing data of the temperature dependence of the thermal properties of the system prevents reaching a quantitative agreement between the measured and calculated scattering data. This modeling approach is essential for the identification of the underlying physical mechanism responsible for the thermo-optical nonlinearity of the metal and should be adopted in all applications of high-temperature nonlinear plasmonics, especially for refractory metals, for both CW and pulsed illumination.

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