Application of the Volterra filter in experimental diffraction data processing

Open Physics ◽  
2003 ◽  
Vol 1 (3) ◽  
Author(s):  
Stanislav Jurečka ◽  
Mária Jurečková
Keyword(s):  
Diffraction Data ◽  
High Frequency ◽  
Digital Filters ◽  
Low Frequency ◽  
Frequency Noise ◽  
X Ray Diffraction ◽  
Volterra Type ◽  
X Ray ◽  
Effective Signal

AbstractThe effective signal in x-ray diffraction analysis of material properties often contains high frequency (noise) and low frequency (trend) components as additive parts. It is necessary to extract the effective signal from the noise to ensure high quality of signal processing. Digital filters of Volterra type are proposed for filtering purposes and a comparison of Volterra filtration implemented on x-ray diffraction data versus results from a set of other digital filters is given.

scholarly journals X-ray diffraction data as a source of the vibrational free-energy contribution in polymorphic systems

IUCrJ ◽  
2019 ◽  
Vol 6 (4) ◽  
pp. 558-571 ◽  
Author(s):  
Phillip Miguel Kofoed ◽  
Anna A. Hoser ◽  
Frederik Diness ◽  
Silvia C. Capelli ◽  
Anders Østergaard Madsen
Keyword(s):  
Thermodynamic Properties ◽  
Normal Mode ◽  
Diffraction Data ◽  
High Frequency ◽  
Low Frequency ◽  
General Question ◽  
Vibrational Entropy ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Frequency Modes

In this contribution we attempt to answer a general question: can X-ray diffraction data combined with theoretical computations be a source of information about the thermodynamic properties of a given system? Newly collected sets of high-quality multi-temperature single-crystal X-ray diffraction data and complementary periodic DFT calculations of vibrational frequencies and normal mode vectors at the Γ point on the yellow and white polymorphs of dimethyl 3,6-dichloro-2,5-dihydroxyterephthalate are combined using two different approaches, aiming to obtain thermodynamic properties for the two compounds. The first approach uses low-frequency normal modes extracted from multi-temperature X-ray diffraction data (normal coordinate analysis), while the other uses DFT-calculated low-frequency normal mode in the refinement of the same data (normal mode refinement). Thermodynamic data from the literature [Yang et al. (1989), Acta Cryst. B45, 312–323] and new periodic ab initio DFT supercell calculations are used as a reference point. Both approaches tested in this work capture the most essential features of the systems: the polymorphs are enantiotropically related, with the yellow form being the thermodynamically stable system at low temperature, and the white form at higher temperatures. However, the inferred phase transition temperature varies between different approaches. Thanks to the application of unconventional methods of X-ray data refinement and analysis, it was additionally found that, in the case of the yellow polymorph, anharmonicity is an important issue. By discussing contributions from low- and high-frequency modes to the vibrational entropy and enthalpy, the importance of high-frequency modes is highlighted. The analysis shows that larger anisotropic displacement parameters are not always related to the polymorph with the higher vibrational entropy contribution.

Theoretically derived thermodynamic properties can be improved by the refinement of low-frequency modes against X-ray diffraction data

2021 ◽  
Author(s):  
Anna Agnieszka Hoser ◽  
Marcin Sztylko ◽  
Damian Trzybiński ◽  
Anders Østergaard Madsen
Keyword(s):  
Thermodynamic Properties ◽  
Dft Calculations ◽  
Diffraction Data ◽  
Molecular Crystals ◽  
Low Frequency ◽  
X Ray Diffraction ◽  
X Ray ◽  
Efficient Approach

A framework for estimation of thermodynamic properties for molecular crystals via refinement of frequencies from DFT calculations against X-ray diffraction data is presented. The framework provides an efficient approach to...

Superstructure formation in the solid solution Sc3Pt3−xIn3 (x = 0–0.93)

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nataliya L. Gulay ◽  
Rolf-Dieter Hoffmann ◽  
Jutta Kösters ◽  
Yaroslav M. Kalychak ◽  
Stefan Seidel ◽  
...  
Keyword(s):  
Solid Solution ◽  
Diffraction Data ◽  
High Frequency ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Platinum Content ◽  
Arc Melting ◽  
Modulation Vector

Abstract The equiatomic indide ScPtIn (ZrNiAl type, space group P 6 ‾ $‾{6}$ 2m) shows an extended solid solution Sc3Pt3–xIn3. Several samples of the Sc3Pt3–xIn3 series were synthesized from the elements by arc-melting and subsequent annealing, or directly in a high frequency furnace. The lowest platinum content was observed for Sc3Pt2.072(3)In3. All samples were characterized by powder X-ray diffraction and their lattice parameters and several single crystals were studied on the basis of precise single crystal X-ray diffractometer data. The correct platinum occupancy parameters were refined from the diffraction data. Decreasing platinum content leads to decreasing a and c lattice parameters. Satellite reflections were observed for the Sc3Pt3–xIn3 crystals with x = 0.31–0.83. These satellite reflections could be described with a modulation vector ( 1 3 , 1 3 , γ ) $\left(\frac{1}{3},\frac{1}{3},\gamma \right)$ ( γ = 1 2 $\gamma =\frac{1}{2}$ c* for all crystals) and are compatible with trigonal symmetry. The interplay of platinum filled vs. empty In6 trigonal prisms is discussed for an approximant structure with space group P3m1.

scholarly journals Diamonds in the rough: a strong case for the inclusion of weak-intensity X-ray diffraction data

2014 ◽  
Vol 70 (5) ◽  
pp. 1491-1497 ◽  
Author(s):  
Jimin Wang ◽  
Richard A. Wing
Keyword(s):  
Electron Density ◽  
Diffraction Data ◽  
Heavy Atom ◽  
Uniform Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Correlation ◽  
Atomic Models ◽  
Weak Intensity

Overwhelming evidence exists to show that the inclusion of weak-intensity, high-resolution X-ray diffraction data helps improve the refinement of atomic models by imposing strong constraints on individual and overall temperatureBfactors and thus the quality of crystal structures. Some researchers consider these data to be of little value and opt to discard them during data processing, particularly at medium and low resolution, at which individualBfactors of atomic models cannot be refined. Here, new evidence is provided to show that the inclusion of these data helps to improve the quality of experimental phases by imposing proper constraints on electron-density models during noncrystallographic symmetry (NCS) averaging. Using electron-density correlation coefficients as criteria, the resolution of data has successfully been extended from 3.1 to 2.5 Å resolution with redundancy-independent mergingRfactors from below 100% to about 310%. It is further demonstrated that phase information can be fully extracted from observed amplitudes throughde novoNCS averaging. Averaging starts with uniform density inside double-shelled spherical masks and NCS matrices that are derived from bound heavy-atom clusters at the vertices of cuboctahedrally symmetric protein particles.

XRD Instrument Sensitivity Results from a Round Robin Study

1991 ◽  
Vol 35 (A) ◽  
pp. 333-340 ◽  
Author(s):  
W.N. Schreiner ◽  
R. Jenkins ◽  
P.F. Dismore
Keyword(s):  
Diffraction Data ◽  
Round Robin ◽  
Data Sets ◽  
X Ray Diffraction ◽  
Diffraction Intensity ◽  
Generic Type ◽  
X Ray ◽  
The Past ◽  
Instrument Sensitivity

During the course of the past ten years the International Centre for Diffraction Data has sponsored a number of “Round Robin” tests to evaluate the quality of experimental X-ray diffraction data [1-5]. The latest of this series, called the Instrument Parameter Round Robin, was designed to evaluate, among other things, relative angularly-dependent sensitivity differences between diffractometers. Previous experiments have indicated that even perfectly aligned diffractometers of the same generic type, do not necessarily give the same set of relative intensities. One objective of the round robin was to quantify the magnitude of the experimental differences between data sets, and to demonstrate a means for external calibration of diffractometers, so that digitized diffraction intensity data obtained from different instruments could be directly compared.

scholarly journals Comparison of the Quality of Protein Crystals Grown by CLPC Seeds Method

Crystals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 501 ◽  
Author(s):  
Li ◽  
Yan ◽  
Liu ◽  
Wu ◽  
Liu ◽  
...  
Keyword(s):  
Diffraction Data ◽  
Protein Crystal ◽  
Protein Crystals ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
High Quality Protein

We present a systematic quality comparison of protein crystals obtained with and without cross-linked protein crystal (CLPC) seeds. Four proteins were used to conduct the experiments, and the results showed that crystals obtained in the presence of CLPC seeds exhibited a better morphology. In addition, the X-ray diffraction data showed that the CLPC seeds method is a powerful tool to obtain high-quality protein crystals. Therefore, we recommend the use of CLPC seeds in preparing high-quality diffracting protein crystals.

HETEROEPITAXIAL GROWTH AND ANNEALING OF γ-AL2O3 THIN FILMS ON SILICON

2002 ◽  
Vol 16 (28n29) ◽  
pp. 4302-4305 ◽  
Author(s):  
LIWEN TAN ◽  
JUN WANG ◽  
QIYUAN WANG ◽  
YUANHUAN YU ◽  
LANYING LIN
Keyword(s):  
High Frequency ◽  
Chemical Vapor ◽  
High Energy ◽  
Annealing Effect ◽  
High Energy Electron ◽  
Heteroepitaxial Growth ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pressure Chemical

The γ- Al 2 O 3 films were grown on Si (100) substrates using the sources of TMA ( Al ( CH 3)3) and O 2 by very low-pressure chemical vapor deposition (VLP-CVD). It has been found that the γ- Al 2 O 3 film has a mirror-like surface and the RMS was about 2.5nm. And the orientation relationship was γ- Al 2 O 3(100)/ Si (100). The thickness uniformity of γ- Al 2 O 3 films for 2-inch epi-wafer was less than 5%. The X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) results show that the crystalline quality of the film was improved after the film was annealed at 1000°C in O 2 atmosphere. The high-frequency C-V and leakage current of Al /γ- Al 2 O 3/ Si capacitor were also measured to verify the annealing effect of the film. The results show that the dielectric constant increased from 4 to 7 and the breakdown voltage for 65-nm-thick γ- Al 2 O 3 film on silicon increases from 17V to 53V.

On the quality of the continuous rotation electron diffraction data for accurate atomic structure determination of inorganic compounds

2018 ◽  
Vol 51 (4) ◽  
pp. 1094-1101 ◽  
Author(s):  
Yunchen Wang ◽  
Taimin Yang ◽  
Hongyi Xu ◽  
Xiaodong Zou ◽  
Wei Wan
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Structural Models ◽  
Electron Diffraction Data ◽  
Data Sets ◽  
X Ray Diffraction ◽  
X Ray ◽  
Continuous Rotation

The continuous rotation electron diffraction (cRED) method has the capability of providing fast three-dimensional electron diffraction data collection on existing and future transmission electron microscopes; unknown structures could be potentially solved and refined using cRED data collected from nano- and submicrometre-sized crystals. However, structure refinements of cRED data using SHELXL often lead to relatively high R1 values when compared with those refined against single-crystal X-ray diffraction data. It is therefore necessary to analyse the quality of the structural models refined against cRED data. In this work, multiple cRED data sets collected from different crystals of an oxofluoride (FeSeO3F) and a zeolite (ZSM-5) with known structures are used to assess the data consistency and quality and, more importantly, the accuracy of the structural models refined against these data sets. An evaluation of the precision and consistency of the cRED data by examination of the statistics obtained from the data processing software DIALS is presented. It is shown that, despite the high R1 values caused by dynamical scattering and other factors, the refined atomic positions obtained from the cRED data collected for different crystals are consistent with those of the reference models refined against single-crystal X-ray diffraction data. The results serve as a reference for the quality of the cRED data and the achievable accuracy of the structural parameters.

The Effect of Indium Surfactant on the Optoelectronic and Structural Properties of MBE Grown Gallium Nitride

2000 ◽  
Vol 618 ◽  
Author(s):  
C.F. Zhu ◽  
W.K. Fong ◽  
B.H. Leung ◽  
C.C. Cheng ◽  
C. Surya ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Power Spectra ◽  
Low Frequency ◽  
Rf Plasma ◽  
Frequency Noise ◽  
Noise Power ◽  
Low Frequency Noise ◽  
X Ray Diffraction ◽  
X Ray ◽  
The One

ABSTRACTGallium nitride films were grown by rf-plasma assisted molecular beam epitaxy. A small indium flux was used as surfactant during the growth. The optical and electrical properties of the films grown with and without In surfactant were characterized by investigating the photoluminescence (PL), high resolution x-ray diffraction (HRXRD) and low-frequency noise power spectra. The sample grown in the presence of In surfactant showed a suppressed yellow luminescence (YL) compared to the one grown without In surfactant. Significant reduction in the full width at half maximum of the GaN (0002) x-ray diffraction peak, indicating a better film quality, was obtained when In surfactant was used during growth. Atomic force microscopy studies show that the root mean squared surface roughness for films grown with and without the In surfactant are 5.86 and 6.99 nm respectively indicating significant improvement in surface morphology. This is attributed to the enhanced 2-dimensional growth by In surfactant. A smaller Hooge parameter was obtained from the low-frequency noise measurement for the sample grown with In surfactant indicating that application of In surfactant led to significant reduction in the trap density of the material.

Nature of Low-Frequency Excess Noise in n-Type Gallium Nitride

2000 ◽  
Vol 622 ◽  
Author(s):  
C. F. Zhu ◽  
W. K. Fong ◽  
B. H. Leung ◽  
C. C. Cheng ◽  
C. Surya
Keyword(s):  
Flicker Noise ◽  
Power Spectra ◽  
Low Frequency ◽  
Excess Noise ◽  
Rf Plasma ◽  
Frequency Noise ◽  
Noise Power ◽  
Frequency Range ◽  
X Ray Diffraction ◽  
X Ray

ABSTRACTLow-frequency noise is investigated in n-type GaN film grown by rf-plasma assisted molecular beam epitaxy. The temperature dependence of the voltage noise power spectra, SV(f), was examined from 400K to 80K in the frequency range between 30Hz and 100KHz, which can be modeled as the superposition of 1/f (flicker) noise G-R noise. At f > 500 Hz the noise is dominated by G-R noise with activation energies of 360meV and 65meV from the conduct band. The results clearly demonstrate the trap origin for both the 1/f noise and G-R noise. At the low-frequency range the fluctuation was dominated by 1/f noise. To determine the origin of the noise we considered both the bulk mobility fluctuation and the trap fluctuation models. Our experimental results showed that rapid thermal annealing (RTA) at 800°C resulted in over one order of magnitude decrease in the Hooge parameter. Annealing at temperatures in excess of 1000°C resulted in significant increase in the noise. Photoluminescence and x-ray diffraction measurements also showed that the crystallinity of the films improved with RTA at 800°C with an accompanying reduction in deep levels. Annealing at 900°C and 1000°C resulted in an increase in the FWHM of the x-ray diffraction indicative of thermal decomposition of the materials. The results are in excellent agreement with the trend of Hooge parameters as a function of annealing temperature, strongly indicating trap origin of the observed 1/f noise.

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