Acta Crystallographica Section A最新文献

A new vision for Acta Crystallographica Section A. 晶体学报A辑的新展望。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-10-17 DOI: 10.1107/S0108767313023702

Simon J L Billinge, Jianwei Miao

引用次数: 0

Nets with collisions (unstable nets) and crystal chemistry. 有碰撞的网(不稳定网)和晶体化学。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-09-12 DOI: 10.1107/S0108767313020655

Olaf Delgado-Friedrichs, Stephen T Hyde, Shin Won Mun, Michael O'Keeffe, Davide M Proserpio

引用次数: 16

Homometry in the light of coherent beams. 相干光束的均匀性。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-09-27 DOI: 10.1107/S0108767313022733

Sylvain Ravy

引用次数: 3

Platonic solids generate their four-dimensional analogues. 柏拉图立体生成它们的四维类似物。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-09-12 DOI: 10.1107/S0108767313021442

Pierre Philippe Dechant

{"title":"Platonic solids generate their four-dimensional analogues.","authors":"Pierre Philippe Dechant","doi":"10.1107/S0108767313021442","DOIUrl":"https://doi.org/10.1107/S0108767313021442","url":null,"abstract":"This paper shows how regular convex 4-polytopes - the analogues of the Platonic solids in four dimensions - can be constructed from three-dimensional considerations concerning the Platonic solids alone. Via the Cartan-Dieudonné theorem, the reflective symmetries of the Platonic solids generate rotations. In a Clifford algebra framework, the space of spinors generating such three-dimensional rotations has a natural four-dimensional Euclidean structure. The spinors arising from the Platonic solids can thus in turn be interpreted as vertices in four-dimensional space, giving a simple construction of the four-dimensional polytopes 16-cell, 24-cell, the F4 root system and the 600-cell. In particular, these polytopes have `mysterious' symmetries, that are almost trivial when seen from the three-dimensional spinorial point of view. In fact, all these induced polytopes are also known to be root systems and thus generate rank-4 Coxeter groups, which can be shown to be a general property of the spinor construction. These considerations thus also apply to other root systems such as A(1)oplus I(2)(n) which induces I(2)(n)oplus I(2)(n), explaining the existence of the grand antiprism and the snub 24-cell, as well as their symmetries. These results are discussed in the wider mathematical context of Arnold's trinities and the McKay correspondence. These results are thus a novel link between the geometries of three and four dimensions, with interesting potential applications on both sides of the correspondence, to real three-dimensional systems with polyhedral symmetries such as (quasi)crystals and viruses, as well as four-dimensional geometries arising for instance in Grand Unified Theories and string and M-theory.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":"69 Pt 6","pages":"592-602"},"PeriodicalIF":1.8,"publicationDate":"2013-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767313021442","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"31813229","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: 15

Distribution rules of systematic absences on the Conway topograph and their application to powder auto-indexing. 康威地形上系统缺位分布规律及其在粉末自动分度中的应用。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-10-01 DOI: 10.1107/S0108767313021740

R Oishi-Tomiyasu

引用次数: 10

More about residual values. 更多关于残值的内容。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-10-02 DOI: 10.1107/S0108767313022514

Julian Henn, Andreas Schönleber

引用次数: 8

Direct phasing of nanocrystal diffraction. 纳米晶衍射的直接相位。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-10-05 DOI: 10.1107/S0108767313023362

Veit Elser

引用次数: 27

C70, C80, C90 and carbon nanotubes by breaking of the icosahedral symmetry of C60. C70, C80, C90和碳纳米管通过打破C60的二十面体对称。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-09-12 DOI: 10.1107/S0108767313021375

Mark Bodner, Jiří Patera, Marzena Szajewska

{"title":"C70, C80, C90 and carbon nanotubes by breaking of the icosahedral symmetry of C60.","authors":"Mark Bodner, Jiří Patera, Marzena Szajewska","doi":"10.1107/S0108767313021375","DOIUrl":"https://doi.org/10.1107/S0108767313021375","url":null,"abstract":"The icosahedral symmetry group H3 of order 120 and its dihedral subgroup H2 of order 10 are used for exact geometric construction of polytopes that are known to exist in nature. The branching rule for the H3 orbit of the fullerene C60 to the subgroup H2 yields a union of eight orbits of H2: four of them are regular pentagons and four are regular decagons. By inserting into the branching rule one, two, three or n additional decagonal orbits of H2, one builds the polytopes C70, C80, C90 and nanotubes in general. A minute difference should be taken into account depending on whether an even or odd number of H2 decagons are inserted. Vertices of all the structures are given in exact coordinates relative to a non-orthogonal basis naturally appropriate for the icosahedral group, as well as relative to an orthonormal basis. Twisted fullerenes are defined. Their surface consists of 12 regular pentagons and 20 hexagons that have three and three edges of equal length. There is an uncountable number of different twisted fullerenes, all with precise icosahedral symmetry. Two examples of the twisted C60 are described. ","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":"69 Pt 6","pages":"583-91"},"PeriodicalIF":1.8,"publicationDate":"2013-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767313021375","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"31813228","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: 14

Comparative study of X-ray charge-density data on CoSb3. CoSb3 x射线电荷密度数据的比较研究。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-10-17 DOI: 10.1107/S0108767313024458

Mette Stokkebro Schmøkel, Lasse Bjerg, Finn Krebs Larsen, Jacob Overgaard, Simone Cenedese, Mogens Christensen, Georg K H Madsen, Carlo Gatti, Eiji Nishibori, Kunihisa Sugimoto, Masaki Takata, Bo Brummerstedt Iversen

{"title":"Comparative study of X-ray charge-density data on CoSb3.","authors":"Mette Stokkebro Schmøkel, Lasse Bjerg, Finn Krebs Larsen, Jacob Overgaard, Simone Cenedese, Mogens Christensen, Georg K H Madsen, Carlo Gatti, Eiji Nishibori, Kunihisa Sugimoto, Masaki Takata, Bo Brummerstedt Iversen","doi":"10.1107/S0108767313024458","DOIUrl":"https://doi.org/10.1107/S0108767313024458","url":null,"abstract":"CoSb3 is an example of a highly challenging case for experimental charge-density analysis due to the heavy elements (suitability factor of ~0.01), the perfect crystallinity and the high symmetry of the compound. It is part of a family of host-guest structures that are potential candidates for use as high-performance thermoelectric materials. Obtaining and analysing accurate charge densities of the undoped host structure potentially can improve the understanding of the thermoelectric properties of this family of materials. In a previous study, analysis of the electron density gave a picture of covalent Co-Sb and Sb-Sb interactions together with relatively low atomic charges based on state-of-the-art experimental and theoretical data. In the current study, several experimental X-ray diffraction data sets collected on the empty CoSb3 framework are compared in order to probe the experimental requirements for obtaining data of high enough quality for charge-density analysis even in the case of very unsuitable crystals. Furthermore, the quality of the experimental structure factors is tested by comparison with theoretical structure factors obtained from periodic DFT calculations. The results clearly show that, in the current study, the data collected on high-intensity, high-energy synchrotron sources and very small crystals are superior to data collected at conventional sources, and in fact necessary for a meaningful charge-density study, primarily due to greatly diminished effects of extinction and absorption which are difficult to correct for with sufficient accuracy.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":"69 Pt 6","pages":"570-82"},"PeriodicalIF":1.8,"publicationDate":"2013-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767313024458","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"31813227","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: 22

Spin line groups. 旋转线群。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2013-11-01 Epub Date: 2013-10-17 DOI: 10.1107/S0108767313022642

Nataša Lazić, Marko Milivojević, Milan Damnjanović

引用次数: 0