Acta Crystallographica Section A最新文献_第2页

Semi-transparent central stop in high-resolution X-ray ptychography using Kirkpatrick–Baez focusing 采用柯克帕特里克-贝兹聚焦的高分辨率x射线照相术中的半透明中央光圈

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-08-14 DOI: 10.1107/S0108767313019612

R. Wilke, M. Vassholz, Tim Salditt

引用次数: 47

Inferring planar disorder in close-packed structures via ε-machine spectral reconstruction theory: examples from simulated diffraction patterns. 用ε-机谱重建理论推断密集结构中的平面无序:模拟衍射图的例子。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-17 DOI: 10.1107/S0108767313008738

D P Varn, G S Canright, J P Crutchfield

{"title":"Inferring planar disorder in close-packed structures via ε-machine spectral reconstruction theory: examples from simulated diffraction patterns.","authors":"D P Varn, G S Canright, J P Crutchfield","doi":"10.1107/S0108767313008738","DOIUrl":"https://doi.org/10.1107/S0108767313008738","url":null,"abstract":"A previous paper detailed a novel algorithm, ε-machine spectral reconstruction theory (εMSR), that infers pattern and disorder in planar-faulted, close-packed structures directly from X-ray diffraction patterns [Varn et al. (2013). Acta Cryst. A69, 197-206]. Here εMSR is applied to simulated diffraction patterns from four close-packed crystals. It is found that, for stacking structures with a memory length of three or less, εMSR reproduces the statistics of the stacking structure; the result being in the form of a directed graph called an ε-machine. For stacking structures with a memory length larger than three, εMSR returns a model that captures many important features of the original stacking structure. These include multiple stacking faults and multiple crystal structures. Further, it is found that εMSR is able to discover stacking structure in even highly disordered crystals. In order to address issues concerning the long-range order observed in many classes of layered materials, several length parameters are defined, calculable from the ε-machine, and their relevance is discussed.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767313008738","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"31516775","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: 11

Digital electron diffraction--seeing the whole picture. 数码电子衍射——看到全貌。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-21 DOI: 10.1107/S0108767313010143

Richard Beanland, Paul J Thomas, David I Woodward, Pamela A Thomas, Rudolf A Roemer

{"title":"Digital electron diffraction--seeing the whole picture.","authors":"Richard Beanland, Paul J Thomas, David I Woodward, Pamela A Thomas, Rudolf A Roemer","doi":"10.1107/S0108767313010143","DOIUrl":"https://doi.org/10.1107/S0108767313010143","url":null,"abstract":"The advantages of convergent-beam electron diffraction for symmetry determination at the scale of a few nm are well known. In practice, the approach is often limited due to the restriction on the angular range of the electron beam imposed by the small Bragg angle for high-energy electron diffraction, i.e. a large convergence angle of the incident beam results in overlapping information in the diffraction pattern. Techniques have been generally available since the 1980s which overcome this restriction for individual diffracted beams, by making a compromise between illuminated area and beam convergence. Here a simple technique is described which overcomes all of these problems using computer control, giving electron diffraction data over a large angular range for many diffracted beams from the volume given by a focused electron beam (typically a few nm or less). The increase in the amount of information significantly improves the ease of interpretation and widens the applicability of the technique, particularly for thin materials or those with larger lattice parameters.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767313010143","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"31516776","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: 14

Primo Levi, William Henry Bragg and the atomic theory of matter. 普里莫·列维，威廉·亨利·布拉格和物质的原子理论。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-08 DOI: 10.1107/S0108767313006508

Davide Viterbo

引用次数: 2

A new interpretation of the σA parameter. 对σA参数的新解释。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-15 DOI: 10.1107/S010876731300768X

B Carrozzini, G L Cascarano, C Giacovazzo, A Mazzone

引用次数: 3

Three-dimensional single-particle imaging using angular correlations from X-ray laser data. 利用x射线激光数据的角相关性进行三维单粒子成像。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-08 DOI: 10.1107/S0108767313006016

Haiguang Liu, Billy K Poon, Dilano K Saldin, John C H Spence, Peter H Zwart

{"title":"Three-dimensional single-particle imaging using angular correlations from X-ray laser data.","authors":"Haiguang Liu, Billy K Poon, Dilano K Saldin, John C H Spence, Peter H Zwart","doi":"10.1107/S0108767313006016","DOIUrl":"https://doi.org/10.1107/S0108767313006016","url":null,"abstract":"Femtosecond X-ray pulses from X-ray free-electron laser sources make it feasible to conduct room-temperature solution scattering experiments far below molecular rotational diffusion timescales. Owing to the ultra-short duration of each snapshot in these fluctuation scattering experiments, the particles are effectively frozen in space during the X-ray exposure. In contrast to standard small-angle scattering experiments, the resulting scattering patterns are anisotropic. The intensity fluctuations observed in the diffraction images can be used to obtain structural information embedded in the average angular correlation of the Fourier transform of the scattering species, of which standard small-angle scattering data are a subset. The additional information contained in the data of these fluctuation scattering experiments can be used to determine the structure of macromolecules in solution without imposing symmetry or spatial restraints during model reconstruction, reducing ambiguities normally observed in solution scattering studies. In this communication, a method that utilizes fluctuation X-ray scattering data to determine low-resolution solution structures is presented. The method is validated with theoretical data calculated from several representative molecules and applied to the reconstruction of nanoparticles from experimental data collected at the Linac Coherent Light Source.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767313006016","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"31515845","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: 44

Tabulation of irreducible representations of the crystallographic space groups and their superspace extensions. 晶体学空间群及其超空间扩展的不可约表示的制表。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-08 DOI: 10.1107/S0108767313007538

Harold T Stokes, Branton J Campbell, Ryan Cordes

{"title":"Tabulation of irreducible representations of the crystallographic space groups and their superspace extensions.","authors":"Harold T Stokes, Branton J Campbell, Ryan Cordes","doi":"10.1107/S0108767313007538","DOIUrl":"https://doi.org/10.1107/S0108767313007538","url":null,"abstract":"New tables of irreducible representations (IRs) are introduced for the 230 crystallographic space groups (SGs) in three-dimensional space, at both special and non-special k vectors, and for their extensions to (3 + d)-dimensional superspace (`superspace-extended SGs' or SSESGs). Neither a tabulation of SG IR matrices for non-special k vectors nor a tabulation of SSESG IR matrices for d > 1 have been previously published. These tabulations are made possible by a new form in which the IR matrices of SGs are separated as a product of a translation part T and a point-operation part P, and where the IR matrices of SSESGs are separated as a product of a phase-shift part Q and a point-operation part P(s). Both T and Q have a simple prescribed form that does not need to be tabulated. Also, the new IR matrices are in a convenient block form which allows one to see by inspection which parts of the matrices and the associated order parameters belong to which arm of the star of k. In addition to complex IR matrices, real physically irreducible representation (PIR) matrices are tabulated. The new IR and PIR tables are available on the ISO-IR website (http://stokes.byu.edu/iso/irtables.php) in both convenient human-readable and computer-readable forms.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767313007538","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"31515846","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: 27

Symmetry group of two special types of carbon nanotori. 两种特殊碳纳米环的对称群。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-22 DOI: 10.1107/S0108767313010325

Mihai D Staic, Alina Petrescu-Nita

引用次数: 9

Incommensurate crystallography without additional dimensions. 没有额外尺寸的不相称晶体学。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-17 DOI: 10.1107/S0108767313005990

Philippe Kocian

引用次数: 1

Application of δ recycling to electron automated diffraction tomography data from inorganic crystalline nanovolumes. δ循环在无机晶体纳米体积电子自动衍射层析成像中的应用。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-07-01 Epub Date: 2013-05-15 DOI: 10.1107/S0108767313009549

Jordi Rius, Enrico Mugnaioli, Oriol Vallcorba, Ute Kolb

{"title":"Application of δ recycling to electron automated diffraction tomography data from inorganic crystalline nanovolumes.","authors":"Jordi Rius, Enrico Mugnaioli, Oriol Vallcorba, Ute Kolb","doi":"10.1107/S0108767313009549","DOIUrl":"https://doi.org/10.1107/S0108767313009549","url":null,"abstract":"δ Recycling is a simple procedure for directly extracting phase information from Patterson-type functions [Rius (2012). Acta Cryst. A68, 399-400]. This new phasing method has a clear theoretical basis and was developed with ideal single-crystal X-ray diffraction data. On the other hand, introduction of the automated diffraction tomography (ADT) technique has represented a significant advance in electron diffraction data collection [Kolb et al. (2007). Ultramicroscopy, 107, 507-513]. When combined with precession electron diffraction, it delivers quasi-kinematical intensity data even for complex inorganic compounds, so that single-crystal diffraction data of nanometric volumes are now available for structure determination by direct methods. To check the tolerance of δ recycling to missing data-collection corrections and to deviations from kinematical behaviour of ADT intensities, δ recycling has been applied to differently shaped nanocrystals of various inorganic materials. The results confirm that it can phase ADT data very efficiently. In some cases even more complete structure models than those derived from conventional direct methods and least-squares refinement have been found. During this study it has been demonstrated that the Wilson-plot scaling procedure is largely insensitive to sample thickness variations and missing absorption corrections affecting electron ADT intensities.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":null,"pages":null},"PeriodicalIF":1.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767313009549","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"31515847","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: 13