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Open AccessArticle

Multiple Diffraction in a Basic Co-Rich Decagonal Al-Co-Ni Quasicrystal

by Changzeng Fan

Metals 2025, 15(12), 1386; https://doi.org/10.3390/met15121386 - 18 Dec 2025

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To reveal its influence on quasicrystal structure analysis, multiple diffraction effects in a basic Co-rich decagonal Al-Co-Ni quasicrystal have been investigated in-house and with synchrotron radiation. Two weak reflections were chosen as the main reflections in the in-house measurements, and 40°

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-scans [...] Read more.

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-scans of one main reflection have been performed with synchrotron radiation. As well as being known for periodic crystals and the icosahedral quasicrystal, it is also observed for this decagonal quasicrystal that the intensity of the main reflection may significantly increase if the simultaneous and the coupling reflections are both strong. The occurrence of multiple diffraction events during collection of a full data set as well as the

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-scans measurements have been studied based on an average structure model and the kinematical multiple diffraction theory. The present experimental and simulation efforts on the effects of multiple diffraction suggest that it is insufficient on its own to explain the discrepancy in weak-reflection intensities; alternative explanations like the phasonic disorder should be paid more attention in future. Full article

(This article belongs to the Special Issue Research Progress of Crystal in Metallic Materials)

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11 pages, 3333 KB

Open AccessArticle

The Limits of X-ray Diffraction Theory

by Paul F. Fewster

Crystals 2023, 13(3), 521; https://doi.org/10.3390/cryst13030521 - 18 Mar 2023

Cited by 13 | Viewed by 12026

Abstract

X-ray diffraction theory allows the interpretation of experiments to build a structural model that fits the collected data. As with any experimental science, the observations are subject to uncertainty through the instrument and user limitations. Similarly, the theory can never be perfectly complete; it will have limits, and therefore the resultant model will have uncertainties associated with it. This article discusses the limits of X-ray kinematical and dynamical diffraction theories. These are not the only theories, but are the most widely used. These theories are often extended to accommodate new findings, which can reach the stage at which their fundamental premise is clouded. At that point, the theory requires a rethink. There should be nothing sacrosanct about a theory; it should represent the best usable explanation that will allow a good interpretation of the data. Both kinematical and dynamical theories assume that the X-rays see an average structure, which is not what a photon experiences. The observed diffraction pattern is the average of the diffraction patterns created by all the photons, which is not the same as the diffraction pattern from the average structure. Accounting for this has a profound influence on the interpretation of the data. Full article

(This article belongs to the Special Issue X-ray Diffraction on Crystalline Materials)

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11 pages, 3498 KB

Open AccessArticle

Simplified Determination of RHEED Patterns and Its Explanation Shown with the Use of 3D Computer Graphics

by Łukasz Kokosza, Jakub Pawlak, Zbigniew Mitura and Marek Przybylski

Materials 2021, 14(11), 3056; https://doi.org/10.3390/ma14113056 - 3 Jun 2021

Cited by 6 | Viewed by 6570

Abstract

The process of preparation of nanostructured thin films in high vacuum can be monitored with the help of reflection high energy diffraction (RHEED). However, RHEED patterns, both observed or recorded, need to be interpreted. The simplest approaches are based on carrying out the Ewald construction for a set of rods perpendicular to the crystal surface. This article describes how the utilization of computer graphics may be useful for realistic reproduction of experimental conditions, and then for carrying out the Ewald construction in a reciprocal 3D space. The computer software was prepared in the Java programing language. The software can be used to interpret real diffractions patterns for relatively flat surfaces, and thus it may be helpful in broad research practice. Full article

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28 pages, 1170 KB

Open AccessArticle

Spin and Polarization in High-Energy Hadron-Hadron and Lepton-Hadron Scattering

by László Jenkovszky

Symmetry 2020, 12(11), 1784; https://doi.org/10.3390/sym12111784 - 28 Oct 2020

Cited by 5 | Viewed by 2693

Abstract

The role of spin degrees of freedom in high-energy hadron-hadron and lepton-hadron scattering is reviewed with emphasis on the dominant role of soft, diffractive, non-perturbative effects. Explicit models based on analyticity and Regge-pole theory, including the pomeron trajectory (gluon exchange in the t channel) are discussed. We argue that there is a single, universal pomeron in Nature, manifest as relatively “soft” or “hard”, depending on the kinematics considered. Both the pomeron and the non-leading (secondary) Regge trajectories, made of quarks are non-linear, complex functions. They are populated by a finite number of resonances: known baryons and mesons in case of the reggeons and hypothetical glueballs in case of the pomeron (“oddballs” on the odderon trajectory). Explicit models and fits are presented that may be used in recovering generalized parton distributions from deeply virtual Compton scattering and electoproduction of vector mesons. Full article

(This article belongs to the Special Issue Advances in Spin Physics)

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13 pages, 2991 KB

Open AccessArticle

Effects of Domain Boundaries on the Diffraction Patterns of One-Dimensional Structures

by Frederic Timmer and Joachim Wollschläger

Condens. Matter 2017, 2(1), 7; https://doi.org/10.3390/condmat2010007 - 31 Jan 2017

Cited by 4 | Viewed by 4606

Abstract

Motivated by diffraction experiments on the (2√3 x √3) R30◦ reconstructed Si(111) surface due to deposition of rare earth elements (Dy, Tb) and silicide formation, we analyse the splitting and non-splitting of superstructure diffraction spots. For this purpose, we model diffraction patterns for one-dimensional structures generated by the binary surface technique and use supercell models to keep the analysis simple. Diffraction patterns are calculated in the framework of the kinematical diffraction theory, and they are analyzed as a function of the domains and domain boundaries. Basic properties of the diffraction pattern are analyzed for model systems of a two-fold and a three-fold periodicity. The rules derived from these calculations are applied to the “real-world” system of Si(111)-(2√3 × √3) R30◦-RESi_x (RE = Dy or Tb). Depending on the combination of domains and domain boundaries of different types, a plethora of different features are observed in the diffraction patterns. These are analyzed to determine the sizes of both domain boundaries and domains from experimentally observed splitting of specific superstructure spots. Full article

(This article belongs to the Special Issue Selected Papers from The 13th Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures (ACSIN 2016))

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