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International Union of Crystallography

The IUCr is an International Scientific Union. Its objectives are to promote international cooperation in crystallography and to contribute to all aspects of crystallography, to promote international publication of crystallographic research, to facilitate standardization of methods, units, nomenclatures and symbols, and to form a focus for the relations of crystallography to other sciences.

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A new generation of storage - ring


xe5003fig1A bright synchrotron source that emits over a wide part of the electromagnetic spectrum from the infrared to hard X-rays is currently being built in Lund, Sweden. The MAX IV facility presents a range of technical challenges for the team putting together its component parts in a storage - ring synchrotron system that will have a circumference of just a few hundred metres. Nevertheless, if these various challenges can be addressed then an entirely new class of experiments that require source brightness and transverse coherence will be possible.

Pedro Tavares and colleagues of Lund University provide details of the obstacles they face [Tavares et al. (2014). J. Synchrotron Rad. 21, 862-877; doi:10.1107/S1600577514011503]. The facility has two electron storage rings that operate at 3 and 1.5 GeV, which Tavares explains are optimized for the hard X-ray and soft X-ray/vacuum ultraviolet spectral ranges, respectively. A linear accelerator, which also operates at 3 GeV, injects into both rings but can also drive X-ray pulses as short as 100 fs.

To confine the total circumference to just 528 m, the 3 GeV ring employs a multibend achromat (MBA) lattice. It is this design feature that gives rise to many of the technical issues that the team hopes to address. First, it needs a large number of magnets per achromat and these need to be compact yet powerful. Secondly, the design leads to small - aperture vacuum chambers that result in low vacuum conductance and the need for distributed pumping as well as for the distributed absorption of heat deposited by the synchrotron radiation. There is also a requirement to accommodate a low main radio frequency (100 MHz) and to lengthen the electron bunches to alleviate multiple scattering within the bunches as well as to avoid collective effects driven by, amongst other effects, the chamber wall resistivity.

The team details solutions to the various problems with regard to the MAX IV 3 GeV ring and presents its lattice design as well as the engineering approaches that will overcome the technical issues. "As the first realisation of a light source based on the MBA concept, the MAX IV 3 GeV ring offers an opportunity for validation of concepts that are likely to be essential ingredients of future diffraction-limited light sources," the team concludes. "Regarding the next steps in the MAX IV Project, we are currently involved with the installation of the 3 GeV ring, and commissioning is planned to start mid - 2015," Tavares told us.

The Tavares paper forms part of the special issue in the Journal of Synchrotron Radiation: Diffraction - Limited Storage Rings and New Science Opportunities. Guest Editors: Mikael Eriksson and J.Friso van der Veen.

 

Posted 30 Oct 2014 

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IUCr news digest 27 October 2014

summits_bloemfonteinThe third IUCr-UNESCO Summit Meeting in the International Year of Crystallography was hosted by Professor André Roodt, Head of the Department of Chemistry, and President of the European Crystallographic Association, at the University of the Free State in Bloemfontein, South Africa.

More than 100 senior researchers, early-career researchers, post-doctoral fellows and students representing more than 40 research groups from 32 universities and more than 20 countries attended the Pan African Summit meeting. The meeting consisted of a 2.5 day conference followed by the 2 day Summit. 

The conference looked at the current state of crystallography in Africa, presented via 15 keynote lectures and additional presentations from some 15 young scientists from English-, French- and Arabic-speaking African regions. The programme of the Summit focused on how to use crystallography as a potential vehicle to expand science in Africa.

Registrations are open for the IUCr-UNESCO OpenLab Hong Kong, which will be held at the HKUST Campus from 3 to 7 December 2014. The main partners of this OpenLab are Agilent Technologies and OlexSys.

The OpenLab HK offers an opportunity to provide impetus to develop the science and its practice in some of the less developed countries of the Asian region. Students from HK, Thailand, Malaysia, Indonesia and Philippines have already applied. The deadline for registration is 31 October 2014. Participation is at no cost; however, a charge of US$300 is necessary as a Residential Fee for a single room on the HKUST campus for 6 nights (2 to 7 December). Some bursaries are available to subsidise the costs of accommodation and, where possible, travel.

Mars has been a subject of fascination and active study since at least the 19th century, and its surface andprofessor_david_l_bish atmosphere have been analysed remotely by optical and spectroscopic methods. The two Viking landers, launched in 1975, ushered in a new era of in situ exploration of Mars, which has continued sporadically since that time. Studies of the surface of Mars culminated in two very successful landed missions, the Mars Exploration Rovers (landed in 2004) and Mars Science Laboratory (landed in 2012). Tremendous technological innovations have come from these missions, but our advances are far greater than these and include new ways to look at our own Earth. To listen to a lecture by Professor David L. Bish, Geological Sciences, Indiana University, Bloomington, USA on the value of exploring Mars to humanity, follow the link below. The event will take place on Tuesday 4 November 2014 at 5.30pm at the Leggate Theatre, Victoria Gallery & Museum, University of Liverpool (Building 421 on the Campus Map), UK.

The lecture is FREE but places are limited. Book now at www.liverpool.ac.uk/events/science-and-society or call +44 151 794 2650.
Posted 28 Oct 2014 

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Towards controlled dislocations

Crystallographic defects or irregularities (known as dislocations) are often found within crystalline materials. Two main types of dislocation exist: edge and screw type. However, dislocations found in real materials tend to be a mix of these two types, resulting in a complex atomic arrangement not found in bulk crystals. The study of these dislocations in semiconductors is probably as old as the science of semiconductors itself, and the technological importance of dislocations can hardly be overstated. From their roles in the way crystals form to their effects on a material’s mechanical, thermal and opto-electronic properties, dislocation and defects govern many aspects of a material’s behaviour. Therefore, it is of great scientific interest to identify and study these structures, and understand their impact on the properties of technologically important materials and devices, such as solar cells, photon detectors and similar semiconductor devices.  

lk5001thumbnail.gifDespite the large amount of theoretical work in this field, experimental knowledge detailing the atomically resolved chemical structure of even the most basic dislocations has just begun to be accessible. A group of scientists from the United States has combined state-of-the-art atomic-resolution Z-contrast imaging and X-ray spectroscopy in a scanning transmission electron microscope (STEM) to analyse two low-elastic-energy stair-rod dislocations in the binary II-VI semiconductor CdTe. CdTe is commercially used in thin-film photovoltaics owing to its ideal electrical properties. The conversion efficiency of CdTe solar cells, which is critical for the industry, has only seen minor developments and improvements over the last 20 years despite intense research activity. Current laboratory records are still shy of the theoretical limits quoted as far back as 1961.  

In the current issue of Acta Crystallographica Section A: Foundations and Advances, Klie and co-workers demonstrate how, with the use of atomic-resolution STEM images and specially tailored Burgers circuits, the structure of these dislocations can be identified [Paulauskas et al. (2014). Acta Cryst. A70; doi:10.1107/S2053273314019639]. The results may lead to the eventual improvement in the conversion efficiency of CdTe solar cells. The analysis presented by the authors can also be applied to study and predict similar structures in other zinc-blende and diamond materials. This study further demonstrates how the new generation of aberration-corrected electron microscopes can advance our understanding of seemingly basic crystal-structure defects.

Posted 17 Oct 2014 

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CODATA Prize 2014 awarded to Professor Sydney Hall

[Professor Sydney R. Hall]Professor Sydney R. Hall, now Emeritus Professor at the University of Western Australia in Perth, Australia, through life-long leadership has resoundingly produced outstanding achievements in the world of scientific and technical data. His efforts have reached beyond crystallographic data and into many other science disciplines. He devised a universal self-defining text archive and retrieval (STAR) file format that evolved into the Crystallographic Information Framework (CIF), a momentous contribution in the area of data characterisation, and well known to structural chemists and biologists in particular as both a data and publications standard.  It enables data validation for articles published by IUCr journals, an approach pioneered by Professor Hall in his role during the 1990s as Editor of Acta Crystallographica Section C: Crystal Structure Communications. The CIF standard has been adopted by journals publishing crystal structure results. It also forms the essential core for data in prominent databases such as the Cambridge Structural Database (> half a million entries, growing by more than 40,000 each year) and the Protein Data Bank (> 100,000 entries, growing by ~ 10,000 per year). These databases are widely used by researchers from many science disciplines. In addition, the STAR File approach is being applied to such diverse applications as botanical taxonomy, quantum chemistry, chemical informatics and biographical databases.

Sydney Hall will receive the Prize at SciDataCon 2014, the International Conference on Data Sharing and Integration for Global Sustainability, in New Delhi, 2-5 November 2014.  This is the continuation of the CODATA Conference series, now co-organised with CODATA’s sister organisation, the ICSU World Data System.

John R. Helliwell and Brian McMahon

From the CODATA web site:

The CODATA Prize is a major biennial award which acknowledges outstanding achievement in the world of scientific and technical data.  The work of Professor Sydney Hall certainly meets these criteria and the CODATA Prize Committee is very pleased to recognise his outstanding contribution.  It is particularly fitting that a crystallographer should be so recognised during the International Year of Crystallography.
Posted 15 Oct 2014 

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The Zürich School of Crystallography 2015: Bring Your Own Crystals

[Zurich School 2013]Time is running out to get your applications in to attend the ever popular Zürich School of Crystallography.

The School, organized and directed by Anthony Linden and Hans-Beat Bürgi, is being hosted by the Department of Chemistry at the University of Zürich, Switzerland. The next course will be taking place from 7 to 20 June 2015. The course is ideally suited to Masters and PhD students and postdocs in the molecular and solid-state sciences who do not have access to crystallographic courses at their own institution.

Participants will gain hands-on experience in the science and art of a routine crystal and molecular structure determination of small molecules through lectures, computer exercises and practical work. Theoretical topics in crystal growth, unit cells, space groups, the phase problem, structure refinement and strategies for dealing with difficult structures will be covered. Practical sessions will cover instrumentation, crystal selection and mounting, data collection and exposure to commonly used software and interpretation of program output to name but a few. During the School, students will have the unique opportunity to use one of the five available X-ray diffractometers to collect data and determine the structure of one of their own compounds that they are currently interested in and that they have not worked on before.

Ten tutors experienced in all aspects of chemical crystallography will be on hand to teach the theoretical and practical aspects of this sometimes complex science. The class usually contains no more than 20 students ensuring plenty of individual tuition and guidance throughout the School. This personal attention is probably one of the most unusual aspects of the School. At the end of the School, participants give a ten minute presentation of the results of their analysis.

Comments from a past student of the School include, “Now I feel more confident in evaluating my crystal structure solutions”. Successfully completing the course also has the added bonus of offering 3 ECT credit points, equivalent to 90 contact hours.

To find out more about the School and to apply please visit here.

Posted 15 Oct 2014 

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Crystallography in Africa

ry5062thumnail.jpgAt present there are active crystallographers in only about 80 countries. The IUCr Executive Committee is keen to change this and promote crystallography globally and in particular in developing regions. The IUCr Crystallography in Africa initiative sets out to increase the number of African countries active in crystallography.

During IYCr2014 another project was mounted to build capacity in crystallography not only in Africa but also in Asia and Latin America. IUCr and UNESCO are running open laboratories (OpenLabs) in more than a dozen developing countries throughout the year in partnership with diffractometer manufacturers. These OpenLabs demonstrate how a diffractometer works to university students and their professors and particularly promote crystallography, which supports most scientific research today. Currently OpenLabs have taken place in Pakistan, Argentina, Morocco, Ghana, Cambodia, Uruguay, Indonesia and Turkey, with more scheduled for this year and with plans to continue the programme once IYCr2014 comes to an end.

See details of the forthcoming IYCr Pan African and South African Summit meeting on Crystallography taking place in Bloemfontein, South Africa between 12 and 17 October 2014.

A recent paper resulting in part from the initiative in Africa has been published in Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials entitled "Two-dimensionally stacked heterometallic layers hosting a discrete chair dodecameric ring of water clusters: synthesis and structural study" [Kenfack Tsobnang et al. (2014). Acta Cryst. B70, 900-902; doi:10.1107/S2052520614019921]. The crystallographers from Cameroon and France have characterized the self-assembly of ionic complexes built around an original water cluster.

Despite numerous research projects over the years, many of the properties of water are still misunderstood. Considering water is one of the simplest compounds in existence and so essential to life, it is fascinating and puzzling at the same time that so little is actually known about its behaviour and properties. The paper published by Patrice Kenfack Tsobnang and colleagues may provide further insight into some of the fascinating properties of water due to its infinite hydrogen-bonded network. This may help researchers understand some of the mystery that still exists in the behaviour of water in nature.

Posted 09 Oct 2014