Acta Crystallographica Section A最新文献_第10页

New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique. 用x射线增程技术高精度测量x射线质量衰减系数的新一致性测试。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-03-01 Epub Date: 2012-01-05 DOI: 10.1107/S0108767311044990

C T Chantler, M T Islam, N A Rae, C Q Tran, J L Glover, Z Barnea

引用次数: 12

Totally unimodular nets. 完全单元化的网络。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-03-01 Epub Date: 2012-02-16 DOI: 10.1107/S0108767312000062

Jean-Guillaume Eon, Davide M Proserpio, Vladislav A Blatov

引用次数: 2

Herbert A. Hauptman (1917-2011). 赫伯特·a·豪普特曼(1917-2011)。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-03-01 Epub Date: 2012-02-16 DOI: 10.1107/S0108767312004011

Charles M Weeks

引用次数: 0

The success story of crystallography. 晶体学的成功故事。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-01-01 Epub Date: 2011-12-20 DOI: 10.1107/S0108767311030303

Dieter Schwarzenbach

{"title":"The success story of crystallography.","authors":"Dieter Schwarzenbach","doi":"10.1107/S0108767311030303","DOIUrl":"https://doi.org/10.1107/S0108767311030303","url":null,"abstract":"Diffractionists usually place the birth of crystallography in 1912 with the first X-ray diffraction experiment of Friedrich, Knipping and Laue. This discovery propelled the mathematical branch of mineralogy to global importance and enabled crystal structure determination. Knowledge of the geometrical structure of matter at atomic resolution had revolutionary consequences for all branches of the natural sciences: physics, chemistry, biology, earth sciences and material science. It is scarcely possible for a single person in a single article to trace and appropriately value all of these developments. This article presents the limited, subjective view of its author and a limited selection of references. The bulk of the article covers the history of X-ray structure determination from the NaCl structure to aperiodic structures and macromolecular structures. The theoretical foundations were available by 1920. The subsequent success of crystallography was then due to the development of diffraction equipment, the theory of the solution of the phase problem, symmetry theory and computers. The many structures becoming known called for the development of crystal chemistry and of data banks. Diffuse scattering from disordered structures without and with partial long-range order allows determination of short-range order. Neutron and electron scattering and diffraction are also mentioned.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":"68 Pt 1","pages":"57-67"},"PeriodicalIF":1.8,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767311030303","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30339873","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

Charge transfer on the metallic atom-pair bond, and the crystal structures adopted by intermetallic compounds. 金属原子对键上的电荷转移及金属间化合物所采用的晶体结构。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-01-01 Epub Date: 2011-11-30 DOI: 10.1107/S0108767311044151

T Rajasekharan, V Seshubai

{"title":"Charge transfer on the metallic atom-pair bond, and the crystal structures adopted by intermetallic compounds.","authors":"T Rajasekharan, V Seshubai","doi":"10.1107/S0108767311044151","DOIUrl":"https://doi.org/10.1107/S0108767311044151","url":null,"abstract":"It has been argued in our recent papers that the heat of formation of intermetallic compounds is mostly concentrated in the nearest neighbor unlike atom-pair bonds, and that the positive term in Miedema's equation is associated with charge transfer on the bond to maintain electroneutrality. In this paper, taking examples of some well populated crystal-structure types such as MgCu(2), AsNa(3), AuCu(3), MoSi(2) and SiCr(3) types, the effect of such charge transfer on the crystal structures adopted by intermetallic compounds is examined. It is shown that the correlation between the observed size changes of atoms on alloying and their electronegativity differences is supportive of the idea of charge transfer between atoms. It is argued that the electronegativity and valence differences need to be of the required magnitude and direction to alter, through charge transfer, the elemental radius ratios R(A)/R(B) to the internal radius ratios r(A)/r(B) allowed by the structure types. Since the size change of atoms on alloying is highly correlated to how different R(A)/R(B) is from the ideal radius ratio for a structure type, the lattice parameters of intermetallic compounds can be predicted with excellent accuracy knowing R(A)/R(B). A practical application of the approach developed in our recent papers to superalloy design is presented.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":"68 Pt 1","pages":"156-65"},"PeriodicalIF":1.8,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767311044151","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30339801","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: 17

Direct phasing from Patterson syntheses by δ recycling. δ循环从帕特森合成中直接相化。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-01-01 Epub Date: 2011-11-17 DOI: 10.1107/S0108767311043145

Jordi Rius

引用次数: 13

Crystallography from Haüy to Laue: controversies on the molecular and atomistic nature of solids 从ha<s:1>到劳厄的晶体学:关于固体分子和原子性质的争论

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-01-01 DOI: 10.1524/zkri.2012.1459

H. Kubbinga

引用次数: 11

Crystallography from Haüy to Laue: controversies on the molecular and atomistic nature of solids. 从ha<s:1>到劳厄的晶体学:关于固体分子和原子性质的争论。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-01-01 Epub Date: 2011-12-20 DOI: 10.1107/S0108767311030315

Henk Kubbinga

引用次数: 12

New version of the theoretical databank of transferable aspherical pseudoatoms, UBDB2011--towards nucleic acid modelling. 可转移非球面伪原子理论数据库的新版本，UBDB2011——迈向核酸建模。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-01-01 Epub Date: 2011-11-17 DOI: 10.1107/S0108767311042176

Katarzyna N Jarzembska, Paulina M Dominiak

{"title":"New version of the theoretical databank of transferable aspherical pseudoatoms, UBDB2011--towards nucleic acid modelling.","authors":"Katarzyna N Jarzembska, Paulina M Dominiak","doi":"10.1107/S0108767311042176","DOIUrl":"https://doi.org/10.1107/S0108767311042176","url":null,"abstract":"The theoretical databank of aspherical pseudoatoms (UBDB) was recently extended with over 100 new atom types present in RNA, DNA and in some other molecules of great importance in biology and pharmacy. The atom-type definitions were modified and new atom keys added to provide a more precise description of the atomic charge-density distribution. X-H bond lengths were updated according to recent neutron diffraction studies and implemented in the LSDB program as well as used for modelling the appropriate atom types. The UBDB2011 databank was extensively tested. Electrostatic interaction energies calculated on the basis of the databank of aspherical atom models were compared with the corresponding results obtained directly from wavefunctions at the same level of theory (SPDFG/B3LYP/6-31G** and SPDFG/B3LYP/aug-cc-pVDZ). Various small complexes were analysed to cover most of the different interaction types, i.e. adenine-thymine and guanine-cytosine with hydrogen bonding, guanine-adenine with stacking contacts, and a group of neutral and charged species of nucleic acid bases interacting with amino acid side chains. The energy trends are well preserved (R(2) > 0.9); however the energy values differ between the two methods by about 4 kcal mol(-1) (1 kcal mol(-1) = 4.184 kJ mol(-1)) on average. What is noticeable is that the replacement of one basis set by another in a purely quantum chemical approach leads to the same electrostatic energy difference, i.e. of about 4 kcal mol(-1) in magnitude. The present work opens up the possibility of applying the UBDB2011 for macromolecules that contain DNA/RNA fragments. This study shows that on the basis of the UBDB2011 databank electrostatic interaction energies can be estimated and structure refinements carried out. However, some method limitations are apparent.","PeriodicalId":7400,"journal":{"name":"Acta Crystallographica Section A","volume":"68 Pt 1","pages":"139-47"},"PeriodicalIF":1.8,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108767311042176","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30339880","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: 87

Disputed discovery: the beginnings of X-ray diffraction in crystals in 1912 and its repercussions. 有争议的发现:1912年晶体中x射线衍射的开始及其影响。

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-01-01 Epub Date: 2011-12-20 DOI: 10.1107/S0108767311039985

Michael Eckert

引用次数: 36