Welcome to the

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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Dr Frank Allen FRSC CChem 1944-2014

It is with great sadness that we announce the death of Frank Allen on 10 November 2014, aged 70.

Frank joined the Chemical Crystallography Group at the University of Cambridge in 1970 and played a pivotal role in the establishment of the Cambridge Structural Database. He went on to become the Scientific Director and then the Executive Director of the Cambridge Crystallographic Data Centre.

Following his retirement in 2008, Frank remained with the CCDC as an Emeritus Research Fellow, enabling him to continue to indulge his passion for structural chemistry.

Frank’s research involved collaboration with many scientists around the world, resulting in over 200 papers. He was also a wonderful teacher, supervising more than 20 doctoral students and introducing many more to structural chemistry through workshops over many years.

His contributions to other influential organisations, his vigorous editorship of Acta Crystallographica, the numerous conferences he organised and presentations he made meant Frank was known to and respected by crystallographers the world over.

Frank has long been a leading figure in international crystallography, and was a wonderful colleague, becoming a friend to all those who worked with him. He will be sadly missed.

This information has been taken from the CCDC website. The original article can be viewed here.  A full obituary will be published in IUCr Journals in due course.

Posted 11 Nov 2014 

research news

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Coherence comes into the fold

vv5079X-rays have been at the heart of imaging since their discovery at the end of the nineteenth century. Now, Pierre Thibault and colleagues at University College London, UK and the Paul Scherrer Institute in Switzerland, hope that a new twist on an old favorite will extend and give them dose-limited resolution and sensitivity through the development of X-ray ptychography.

X-ray ptychography is a scanning coherent diffractive imaging technique, the team explains. The technique first suggested in the 1970s involves illuminating the sample with a structured, often confined source and measuring the resulting diffraction pattern for different overlapping positions of the sample, the term is from the Greek "fold" and "writing". Ultimately, ptychography promises to solve the diffraction-pattern phase problem in X-ray studies.

Coherent diffractive imaging (CDI) techniques, of which ptychography is just one, are all underpinned by the lack of a lens to focus the image. Instead of focusing, a mathematical algorithm is used to reconstruct the image of the sample from the collected diffraction patterns. Such a lensless system thus bypasses many of the technical constraints of lenses, which for X-rays are often inefficient, may introduce aberrations, and strongly limit resolution. Lensless, however, means phase is lost, which is where the overlapping folds of ptychography are exploited.

"Ptychography may approach imaging speeds familiar from full-field methods while retaining its inherently quantitative nature and metrological versatility," the team explains Thibault et al. (2014). J. Synchrotron Rad. 21,1011-1018; doi:10.1107/S1600577514015343. "Beyond promises of high throughput, spectroscopic applications in three dimensions become feasible, as do measurements of sample dynamics through time-resolved imaging or careful characterization of decoherence effects." The team suggests that additional technological and analytical advances in bright X-ray sources are now needed to help this field mature and to allow it to enter the realm of high-throughput studies and even three-dimensional spectroscopy.

"Ptychography's active development and sustained rate of successes hints at its potential as an important player in contemporary questions on data acquisition strategies, information content and feature extractions," the team reports, hinting that so-called "big data" methods of the kind usually reserved for particle physics and high-speed tomography, will come to the fore.

"In a way there are many next steps," Thibault told the IUCr. "In the paper we mention 'quantitative improvements', namely improve speed and size of field of view, and 'qualitative improvements', or improving resolution and sensitivity. Beyond this, the goal would be moving to four dimensions, that is adding one extra axis, either spectrum (spectro-tomography) or time (tomographic movies).

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

Posted 17 Nov 2014 

press release

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2014 Nobel Prize, Blue Light Emitting Diode and Crystal Growth

Figure 1: 2014 Nobel Prize winners for Physics
On 7 October 2014 The Royal Swedish Academy of Sciences announced that the Nobel Prize in Physics for 2014 was awarded to three Japanese-born scientists, Isamu Akasaki (now at Meijo University and Nagoya University, Japan), Hiroshi Amano (now at Nagoya University, Japan) and Shuji Nakamura (now at University of California, Santa Barbara, USA). The award is “for the invention of efficient blue light-emitting diodes (LED) which has enabled bright and energy-saving white light sources".

Epitaxial layers of gallium nitride (GaN) – material that exists in the laboratory only – on single-crystal sapphire substrate produce a blue light which can be converted to white light using a phosphor coating. Today these new LEDs are replacing traditional light bulbs and fluorescent tubes worldwide. The white LED lamps are bright, efficient and long lasting. They have improved the quality of life of billions of people around the world: owing to low power requirements these lamps can be powered by cheap, local, solar energy. This discovery directly benefits all of us.

A great deal of information about the Nobel Prize Winners, the blue light emitting diode and its advantages for the whole world can be found in the scientific literature and on the internet. There are interviews, press releases and popular articles.

The reason why we are writing this note is to stress how important to this world-changing discovery is the challenging crystal growth and epitaxial deposition work performed at the beginning of the success path.

To achieve the next step, leading to a high efficiency laser, a new, reliable method of obtaining bulk single crystals of GaN had to be created, implemented and become affordable. This is happening right now as large, high quality GaN crystals are being grown by either high-pressure or amonothermal methods. As this is achieved, many other obstacles, from cutting the bulk crystal in a specific orientation to reducing the number of dislocations, still have to be overcome.

Figure 2: Gallium nitride crystal. Courtesy of the archives of the IWC Sciences
The crystal-growth community recognized the meaningful achievements of these Nobelists with important awards a long time ago. Professor Akasaki received the Laudise Prize in 1998 from the International Organization for Crystal Growth, for his pivotal contributions to the epitaxial growth of group III nitrides, including the use of buffer layers and the development of p-type GaN. In 2007 Professor Nakamura was awarded the prestigious Czochralski Medal as a Polish Society for Crystal Growth nominee, for discovering the technique to create new p-type semiconductor annealing magnesium-doped GaN without hydrogen presence and making the white LED possible.
Figure 3: Final of the Spanish schools crystallisation competition

For many years the IUCr has regularly and generously supported crystal-growth schools and conferences around the world an example can be seen here. These meetings act as forums where new ideas can be formed, discussed and promoted. In the time of scientific budget cuts and limits on basic research in many countries these IUCr activities, as well as those such as the international crystal growth competition for elementary and high-school students, create new interest in the old art of growing crystals. These activities build solid scientific foundations within the future generation of researchers, who – now in their school years – cannot only enjoy the happiness of creating something new and very material: the crystal, but also – and this is extremely important at any age – be applauded and recognized for doing it.

Hanna Dabkowska and Andrea Zappettini
IUCr Commission on Crystal Growth and Characterization of Materials
Posted 20 Nov 2014

research news

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A laboratory grade hybrid pixel detector

bm0070thumbnailThe United Nations proclaimed 2014 the International Year of Crystallography. Due to many of the activities and events taking place throughout the year, it is obvious, more so than in previous years, how crystallography strengthens and enriches all natural sciences. Take for example the breathtaking developments at modern large scale facilities, like third generation synchrotrons, X-ray free-electron lasers and neutron spallation sources, and the various remarkable improvements recently made to home facilities. The sealed X-ray tube has been almost totally replaced today by reliable microfocus or rotating anode sources, stronger by many orders of magnitude when compared to W. C. Röntgen's original device. The same is valid for detector technology, where the original film or scintillation detector, even the image plate, is nowadays almost totally substituted by charge-coupled devices (CCDs, CMOSs). Even they will become outdated very soon when we look at the most recent developments of the single-photon counting hybrid pixel area detector.

This new class of detector combines the virtues of speed of an area detector with the advantageous low noise and extremely high dynamic range of a point detector. The first pixel detectors have been designed and optimized for use with synchrotrons (e.g. PILATUS or EIGER from Dectris, or XPAD from imXPAD). Unfortunately, due partly to cost, data collection and software integration issues, these detectors have not yet reached the typical university laboratory. That is until now [Wenger et al. (2014). Acta Cryst. B70, 783-791; doi: 10.1107/S2052520614017338]. For the first time a group of authors present a pixel detector mounted on a commercial goniometer, equipped with a microfocus X-ray source, to generate high-resolution X-ray data.

The researchers have shown in the paper that high quality diffraction data suitable for accurate charge density studies can be collected by following their set-up.

The charge-density community will be eager to see further developments from this team such as a reduction in data acquisition time, addressing blind detector areas and improved data reduction to tackle estimated systematic errors and intensity variances.

This news story is a short excerpt taken from the commentary [Stalke (2014). Acta Cryst. B70, 781-782; doi: 10.1107/S2052520614021349].

Posted 06 Nov 2014 


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100th Research Communication published in Acta Crystallographica Section E

research communicationsThe relaunch of Acta Crystallographica Section E (http://journals.iucr.org/e) in June this year (2014) saw the publication of the first papers in the new Research Communication format designed to bring out the science behind the structure determination.

Reports are no longer limited to a short description of a single structure and figures are no longer relegated to the Supporting information. We are delighted to see that an increasing number of authors are choosing to publish their work as a Research Communication, with the numbers of these articles increasing every month. The November issue includes the one hundredth paper to be published in this format, so what better time to celebrate the great breadth in the range and scope of the Research Communications published so far?

Authors are positively encouraged to report and discuss related structures in a single Research Communication rather than publishing a series of short structural reports. We are pleased to see that papers reporting two structures are a now regular feature and one three-structure paper has been published. Authors have made the most of the opportunity to include extra tables and figures in the published paper to illustrate their results and enhance the discussion of the underlying science.

We would like to see even more of our authors old and new submit to the journal in this format. Our editors and many of our authors already take advantage of the IUCr's publCIF software to write and edit their papers using a word-processing environment. publCIF takes a crystallographic information file (CIF) and prepares a formatted paper (preprint) in the Research Communication style. The CIF and the preprint are presented side-by-side and can both be edited - changes made to one are applied to the other as you type. publCIF also includes many useful editorial tools to help you write your paper. It can be used to add data items required for publication, prepare standard and customized geometry tables, check your CIF for both syntax and completeness, print or export a preprint of your paper, check the references and more. Using publCIF, a Research Communication can be produced with just a little extra effort. Be sure to use the latest version of publCIF, which is available to download free of charge from http://publcif.iucr.org .

A large part of the success of the new Research Communication format is down to our dedicated team of Co-editors who are doing an excellent job in advising authors how to promote their science. On behalf of the Section Editors of Acta E, I would like to take this opportunity to thank them for helping make Acta Crystallographica Section E the obvious choice for disseminating the results of the excellent crystallography that is being carried out by our authors worldwide.

This announcement is a short excerpt taken from the editorial [Stoeckli-Evans (2014). Acta Cryst. E70, 454-455; doi:10.1107/S1600536814023393].

See our earlier news story covering Acta Crystallographica Section E editorial changes here

Posted 03 Nov 2014 

research news

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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