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Lattice symmetry relaxation as a cause for anisotropic line broadening and peak shift in powder diffraction. 晶格对称性松弛是粉末衍射中各向异性线变宽和峰值移动的原因。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-11-01 Epub Date: 2024-10-03 DOI: 10.1107/S2053273324008799
Miguel Gregorkiewitz, Alice Boschetti
{"title":"Lattice symmetry relaxation as a cause for anisotropic line broadening and peak shift in powder diffraction.","authors":"Miguel Gregorkiewitz, Alice Boschetti","doi":"10.1107/S2053273324008799","DOIUrl":"10.1107/S2053273324008799","url":null,"abstract":"<p><p>In powder diffraction, lattice symmetry relaxation causes a peak to split into several components which are not resolved if the degree of desymmetrization is small (pseudosymmetry). Here the equations which rule peak splitting are elaborated for the six minimal symmetry transitions, showing that the resulting split peaks are generally broader and asymmetric, and suffer an hkl-dependent displacement with respect to the high-symmetry parent peak. These results will be of help in Rietveld refinement of pseudosymmetric structures where an exact interpretation of peak deformation is required.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"439-445"},"PeriodicalIF":1.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11532927/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142363543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Symmetries and symmetry-generated averages of elastic constants up to the sixth order of nonlinearity for all crystal classes, isotropy and transverse isotropy. 所有晶体类别、各向同性和横向各向同性的非线性六阶以下弹性常数的对称性和对称性产生的平均值。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-11-01 Epub Date: 2024-10-15 DOI: 10.1107/S2053273324007666
Rodion Sergeyevich Telyatnik
{"title":"Symmetries and symmetry-generated averages of elastic constants up to the sixth order of nonlinearity for all crystal classes, isotropy and transverse isotropy.","authors":"Rodion Sergeyevich Telyatnik","doi":"10.1107/S2053273324007666","DOIUrl":"10.1107/S2053273324007666","url":null,"abstract":"<p><p>Algebraic expressions for averaging linear and nonlinear stiffness tensors from general anisotropy to different effective symmetries (11 Laue classes elastically representing all 32 crystal classes, and two non-crystalline symmetries: isotropic and cylindrical) have been derived by automatic symbolic computations of the arithmetic mean over the set of rotational transforms determining a given symmetry. This approach generalizes the Voigt average to nonlinear constants and desired approximate symmetries other than isotropic, which can be useful for a description of textured polycrystals and rocks preserving some symmetry aspects. Low-symmetry averages have been used to derive averages of higher symmetry to speed up computations. Relationships between the elastic constants of each symmetry have been deduced from their corresponding averages by resolving the rank-deficient system of linear equations. Isotropy has also been considered in terms of generalized Lamé constants. The results are published in the form of appendices in the supporting information for this article and have been deposited in the Mendeley database.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"394-404"},"PeriodicalIF":1.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142453746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Structure of face-centred icosahedral quasicrystals with cluster close packing. 具有团簇紧密堆积的面心二十面体准晶体的结构。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-11-01 Epub Date: 2024-09-30 DOI: 10.1107/S2053273324008568
Tsunetomo Yamada, Hiroyuki Takakura, Akiji Yamamoto
{"title":"Structure of face-centred icosahedral quasicrystals with cluster close packing.","authors":"Tsunetomo Yamada, Hiroyuki Takakura, Akiji Yamamoto","doi":"10.1107/S2053273324008568","DOIUrl":"10.1107/S2053273324008568","url":null,"abstract":"<p><p>A 6D structure model for face-centred icosahedral quasicrystals consisting of so-called pseudo-Mackay and mini-Bergman-type atomic clusters is proposed based on the structure model of the Al<sub>69.1</sub>Pd<sub>22</sub>Cr<sub>2.1</sub>Fe<sub>6.8</sub> 3/2 cubic approximant crystal (with space group Pa3, a = 40.5 Å) [Fujita et al. (2013). Acta Cryst. A69, 322-340]. The cluster centres form an icosahedral close sphere packing generated by the occupation domains similar to those in the model proposed by Katz & Gratias [J. Non-Cryst. Solids (1993), 153-154, 187-195], but their size is smaller by a factor τ<sup>2</sup> [τ = (1 + (5)<sup>1/2</sup>)/2]. The clusters cover approximately 99.46% of the atomic structure, and the cluster arrangement exhibits 15 and 19 different local configurations, respectively, for the pseudo-Mackay and mini-Bergman-type clusters. The occupation domains that generate cluster shells are modelled and discussed in terms of structural disorder and local reorganization of the cluster arrangements (phason flip).</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"422-438"},"PeriodicalIF":1.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11532924/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142337536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On the principle of reciprocity in inelastic electron scattering. 关于非弹性电子散射中的互易原理。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-11-01 Epub Date: 2024-10-21 DOI: 10.1107/S2053273324009550
Budhika G Mendis
{"title":"On the principle of reciprocity in inelastic electron scattering.","authors":"Budhika G Mendis","doi":"10.1107/S2053273324009550","DOIUrl":"10.1107/S2053273324009550","url":null,"abstract":"<p><p>In electron microscopy the principle of reciprocity is often used to imply time reversal symmetry. While this is true for elastic scattering, its applicability to inelastic scattering is less well established. From the second law of thermodynamics, the entropy for a thermally isolated system must be constant for any reversible process. Using entropy and statistical fluctuation arguments, it is shown that, while reversibility is possible at the microscopic level, it becomes statistically less likely for higher energy transfers. The implications for reciprocal imaging modes, including energy loss and energy gain measurements, as well as Kainuma's reciprocal wave model are also discussed.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"457-459"},"PeriodicalIF":1.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11532925/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142453744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Prices of IUCr journals. IUCr 期刊的价格。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-11-01 Epub Date: 2024-10-31 DOI: 10.1107/S2053273324010404
{"title":"Prices of IUCr journals.","authors":"","doi":"10.1107/S2053273324010404","DOIUrl":"https://doi.org/10.1107/S2053273324010404","url":null,"abstract":"<p><p>IUCr Journals subscription prices for 2025.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":"80 Pt 6","pages":"464-465"},"PeriodicalIF":1.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142566588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Influence of device configuration and noise on a machine learning predictor for the selection of nanoparticle small-angle X-ray scattering models. 设备配置和噪声对用于选择纳米粒子小角 X 射线散射模型的机器学习预测器的影响。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-11-01 Epub Date: 2024-09-23 DOI: 10.1107/S2053273324007988
Nicolas Monge, Massih Reza Amini, Alexis Deschamps
{"title":"Influence of device configuration and noise on a machine learning predictor for the selection of nanoparticle small-angle X-ray scattering models.","authors":"Nicolas Monge, Massih Reza Amini, Alexis Deschamps","doi":"10.1107/S2053273324007988","DOIUrl":"10.1107/S2053273324007988","url":null,"abstract":"<p><p>Small-angle X-ray scattering (SAXS) is a widely used method for nanoparticle characterization. A common approach to analysing nanoparticles in solution by SAXS involves fitting the curve using a parametric model that relates real-space parameters, such as nanoparticle size and electron density, to intensity values in reciprocal space. Selecting the optimal model is a crucial step in terms of analysis quality and can be time-consuming and complex. Several studies have proposed effective methods, based on machine learning, to automate the model selection step. Deploying these methods in software intended for both researchers and industry raises several issues. The diversity of SAXS instrumentation requires assessment of the robustness of these methods on data from various machine configurations, involving significant variations in the q-space ranges and highly variable signal-to-noise ratios (SNR) from one data set to another. In the case of laboratory instrumentation, data acquisition can be time-consuming and there is no universal criterion for defining an optimal acquisition time. This paper presents an approach that revisits the nanoparticle model selection method proposed by Monge et al. [Acta Cryst. (2024), A80, 202-212], evaluating and enhancing its robustness on data from device configurations not seen during training, by expanding the data set used for training. The influence of SNR on predictor robustness is then assessed, improved, and used to propose a stopping criterion for optimizing the trade-off between exposure time and data quality.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"405-413"},"PeriodicalIF":1.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11532926/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142277439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Periodic diffraction from an aperiodic monohedral tiling - the Spectre tiling. Addendum. 来自非周期性单面体平铺的周期性衍射--Spectre平铺。补遗。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-11-01 Epub Date: 2024-10-08 DOI: 10.1107/S2053273324008945
Craig S Kaplan, Michael O'Keeffe, Michael M J Treacy
{"title":"Periodic diffraction from an aperiodic monohedral tiling - the Spectre tiling. Addendum.","authors":"Craig S Kaplan, Michael O'Keeffe, Michael M J Treacy","doi":"10.1107/S2053273324008945","DOIUrl":"10.1107/S2053273324008945","url":null,"abstract":"<p><p>This article describes the diffraction pattern (2-periodic Fourier transform) from the vertices of a large patch of the recently discovered `Spectre' tiling - a strictly chiral aperiodic monotile. It was reported recently that the diffraction pattern of the related weakly chiral aperiodic `Hat' monotile was 2-periodic with chiral plane-group symmetry p6 [Kaplan et al. (2024). Acta Cryst. A80, 72-78]. The diffraction periodicity arises because the Hat tiling is a systematic aperiodic deletion of vertices from the 2-periodic hexagonal mta tiling. Despite the similarity of the Hat and Spectre tilings, the Spectre tiling is not aligned with a 2-periodic lattice, and its diffraction pattern is non-periodic with chiral point symmetry 6 about the origin.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"460-463"},"PeriodicalIF":1.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142386489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Stability of inorganic ionic structures: the uniformity approach. 无机离子结构的稳定性：均匀性方法。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-11-01 Epub Date: 2024-10-14 DOI: 10.1107/S2053273324009008
Alexander P Shevchenko, Vladislav A Blatov
{"title":"Stability of inorganic ionic structures: the uniformity approach.","authors":"Alexander P Shevchenko, Vladislav A Blatov","doi":"10.1107/S2053273324009008","DOIUrl":"10.1107/S2053273324009008","url":null,"abstract":"<p><p>The crystal structure uniformity is numerically estimated as the standard deviation of the crystal space quantizer 〈G<sub>3</sub>〉. This criterion has been applied to explore the uniformity of ionic sublattices in 21465 crystal structures of inorganic ionic compounds. In most cases, at least one kind of sublattice (whole ionic lattice, cationic or anionic sublattice) was found to be highly uniform with a small 〈G<sub>3</sub>〉 value. Non-uniform structures appeared to be either erroneous or essentially non-ionic. As a result, a set of uniformity criteria is proposed for the estimation of the stability of ionic crystal structures.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"446-456"},"PeriodicalIF":1.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142453745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Superstructure reflections in tilted perovskites. 倾斜过氧化物中的超结构反射。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-09-01 Epub Date: 2024-07-26 DOI: 10.1107/S2053273324007113
Richard Beanland, Robin Sjökvist
{"title":"Superstructure reflections in tilted perovskites.","authors":"Richard Beanland, Robin Sjökvist","doi":"10.1107/S2053273324007113","DOIUrl":"10.1107/S2053273324007113","url":null,"abstract":"<p><p>The superstructure spots that appear in diffraction patterns of tilted perovskites are well documented and easily calculated using crystallographic software. Here, by considering a distortion mode as a perturbation of the prototype perovskite structure, it is shown how the structure-factor equation yields Boolean conditions for the presence of superstructure reflections. This approach may have some advantages for the analysis of electron diffraction patterns of perovskites.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"387-390"},"PeriodicalIF":1.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11363165/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141755822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On uniform edge-n-colorings of tilings. 关于倾斜的均匀边缘-n-着色。
IF 1.9 4区 材料科学
Acta Crystallographica Section A: Foundations and Advances Pub Date : 2024-09-01 Epub Date: 2024-07-29 DOI: 10.1107/S2053273324005643
Agatha Kristel Abila, Ma Louise Antonette De Las Peñas, Mark Tomenes
{"title":"On uniform edge-n-colorings of tilings.","authors":"Agatha Kristel Abila, Ma Louise Antonette De Las Peñas, Mark Tomenes","doi":"10.1107/S2053273324005643","DOIUrl":"10.1107/S2053273324005643","url":null,"abstract":"<p><p>An edge-n-coloring of a uniform tiling {cal T} is uniform if for any two vertices of {cal T} there is a symmetry of {cal T} that preserves the colors of the edges and maps one vertex onto the other. This paper gives a method based on group theory and color symmetry theory to arrive at uniform edge-n-colorings of uniform tilings. The method is applied to give a complete enumeration of uniform edge-n-colorings of the uniform tilings of the Euclidean plane, for which the results point to a total of 114 colorings, n = 1, 2, 3, 4, 5. Examples of uniform edge-n-colorings of tilings in the hyperbolic plane and two-dimensional sphere are also presented.</p>","PeriodicalId":106,"journal":{"name":"Acta Crystallographica Section A: Foundations and Advances","volume":" ","pages":"367-378"},"PeriodicalIF":1.9,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141786469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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