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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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Registration for Summer School on Mathematical Crystallography now open

The registration for the Summer School on Mathematical Crystallography (MaThCryst), due to be held in Nancy between 3rd and 7th June 2019, is now open.

Deadline for Registration Application: 31st March 2019

For further information, please visit:

Posted 14 Jan 2019 

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Special issue on mineralogical crystallography

[B cover Dec 18]For many centuries crystallography and mineralogy were part of a single discipline, and it was impossible to separate one from the other. In fact even the early works of Theophrastus (On Stones) and Pliny's Natural History show that the beginnings of both sciences have the same roots. In fact, crystallography grew out of mineralogy because in Steno's time the only crystals available for study were those of minerals. In the 20th century, however, the two sciences went their separate ways, but even today crystallographic research is an important part of mineralogy and mineralogical research is still an important part of crystallography. The December 2018 issue of Acta Cryst. B includes a special issue devoted to mineralogical crystallography and collects some important contributions that demonstrate the diversity of crystallographic ideas and methods developed to solve valuable issues in mineralogy.

There are some 5 500 (and growing) different mineral species known today [1] compared with more than 1 200 000 biological species described so far! Some of these mineral species are rare and occur in only a few localities, whereas others crystallize in the range of millions of tons in the Earth's crust. The latter are called 'rock-forming minerals' and their study is of utmost importance for our understanding of the behaviour of rocks on and beneath the Earth's surface.

[1] Pasero, M. (2018). The new IMA list of minerals, accessed 4 December 2018.

Sergey V. Krivovichev, Janusz Lipkowski and Stuart J. Mills
Guest Editors

Posted 21 Dec 2018

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Jenny Martin to lead University of Wollongong's research and innovation strategy

[Jenny Martin]

IUCr Executive Committee member Jenny Martin has been appointed as Deputy Vice-Chancellor (Research and Innovation) by the University of Wollongong (UOW), Australia. The current director of the Griffith Institute for Drug Discovery at Griffiths University will pursue a research strategy that is “values-based” from next March.

“My vision is for a research strategy that encompasses the values that I hold dear: excellence, respect, integrity and collegiality,” Professor Martin said. “In a high-performing research organisation like UOW we expect to recruit and retain researchers of the highest calibre, and that means providing the support and opportunity for early-career, mid-career and senior researchers to pursue excellence. I also want to bring an element of entrepreneurship and innovation into everything that we do, and I am excited about the opportunity to engage with industry, government and the community." She added that she was also looking forward to working with dedicated and highly talented people from all disciplines - across the arts, humanities, social sciences, engineering, information sciences, business, law as well as science, medicine and health. “That breadth of knowledge, innovation and creativity takes me back to my Oxford days when I was living in college with students from the humanities, with archaeologists and political scientists and engineers. I loved the diversity and the opportunity to communicate with people across discipline boundaries. That is where the greatest innovations occur.”

Professor Martin was made a Companion of the Order of Australia earlier this year for “eminent service to scientific research, particularly in the field of biochemistry and protein crystallography applied to drug-resistant bacteria, as a role model, and as an advocate for gender equality in science”. She is also a Fellow of the Australian Academy of Science, current President of the Asian Crystallographic Association and a former Editor of Acta Cryst. D.

For more information, please see here.

Posted 18 Dec 2018 

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Special issue on Polyoxometalates

[me0669]The November 2018 issue of Acta Crystallographica Section C Structural Chemistry marks a special anniversary of an exciting class of inorganic compounds: polyoxometalates (POMs). In their Guest Editorial, José Ramón Galán-Mascarós and Ulrich Kortz note that the very first POM structure, the so-called Keggin ion ([PW12O40]3−), was structurally characterized by James F. Keggin 85 years ago in 1933 using powder X-ray diffraction. This was an important breakthrough for POM chemistry, as from then on structural aspects became more relevant and allowed the field to be developed more rationally. In the same year, Michael T. Pope was born, who went on to publish the book Heteropoly and Isopoly Oxometalates in 1983, widely agreed still to be the best introductory text to the field.

During the last half century or so, the development of POM chemistry has benefitted tremendously from single-crystal X-ray diffraction. Besides structural aspects, the study of the physicochemical properties of POMs has developed tremendously in recent decades. The multitude of attractive properties includes controllable size, composition, charge density, redox potential, acid strength, high thermal stability in the solid state, solubility in polar/nonpolar solvents and reversible electron/proton storage. Such versatility renders POMs of interest for academic and industrial applications, especially in catalysis but also in fields such as medicine, magnetism, photochemistry and materials science.

It is also worth mentioning how POM chemistry has contributed to the development of crystallography itself. The presence of POMs (in particular heteropolytungstates) in solution often allows large biomolecules to be crystallized, and facilitates X-ray structure solution and refinement due to their high symmetry, robust mol­ecular structure and heavy-atom content. The history of POMs has progressed from the seminal work of Keggin (working under the supervision of Lawrence Bragg and influenced by Linus Pauling) developing powder X-ray diffraction analysis in the early 20th century, to the role of POMs as cocrystallizing agents for large biologically relevant molecules, such as ribosomes, finally leading to the 2009 Nobel Prize in Chemistry (Ramakrishnan, Steitz and Yonath).

The contributions to this special issue on POMs provide an excellent overview of the current state of the subject, as well as providing updates to current research. Acta C is transforming from a structural (XRD) solid-state journal to a more general journal covering all aspects of structural chemistry, and the Guest Editors hope that this special issue on POMs will assist the journal in achieving its goals.

Posted 06 Nov 2018

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The importance of careful refinement

[fabry]

A large number of structural determinations of compounds containing 2-hydroxy-3,5-dinitrobenzoic acid and its various deprotonated forms, 2-hydroxy-3,5-dinitrobenzoate or 2-carboxy-4,6-dinitrophenolate, are biased. The reason for this follows from incorrectly applied constraints or restraints on the bridging hydrogen, which is involved in an intramolecular hydrogen bond between neighbouring carboxylic/carboxylate and oxo/hydroxy groups. This hydrogen bond belongs to the category of resonance-assisted hydrogen bonds. The position of the bridging hydrogen seems to be dependent on the pKa(base), though with some exceptions. A stronger basicity enhances the probability of the presence of a phenolate. The problem of the location and refinement of such a bridging hydrogen, as well as that of the hydrogen atoms involved in the hydroxy group, and primary and secondary amine groups, is discussed in a recent article by Fábry [Acta Cryst. (2018). E74, 1344-1357]. It appears that the best model, in many cases, is obtained by fixing the hydrogen-atom positions found in a difference electron-density map while refining its isotropic displacement parameter.

"It is almost futile to state that modern automated diffractometers have enabled single-crystal X-ray structure analysis to become widely applied even by non-experts," commented Dr Fábry. "At the same time, however, it is important to emphasize that a large number of structure determinations of even simple molecules suffer from defects that are caused by inappropriately applied constraints or restraints. These defects bias not only the structure determinations themselves but also - more importantly - the overall information contained in the crystallographic databases. The present study of a whole family of the title molecules demonstrates the importance of careful refinement as well as of inspection of difference electron-density maps. I hope that this experience will reach especially those scientists for whom crystallography is not their specialization but nevertheless use it in their studies."

Posted 14 Sep 2018

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Simulating cold aqueous environments on Earth and other planetary bodies

[gj5209]Liquid oceans and ice caps, along with ice crusts, have long been considered defining features of the Earth, but space missions and observations have shown that they are in fact common features among many of the solar system's outer planets and their satellites. Interactions with rock-forming materials have produced saline oceans not dissimilar in many respects to those on Earth, where mineral precipitation within frozen seawater plays a significant role in both determining global properties and regulating the environment in which a complex ecosystem of extremophiles exists. As water is considered an essential ingredient for life, the presence of oceans and ice on other solar system bodies is of great astrobiological interest. However, the details surrounding mineral precipitation in freezing environments are still poorly constrained, owing to the difficulties of sampling and ex situ preservation for laboratory analysis, meaning that predictive models have limited empirical underpinnings.

To address this, the design and performance characterization of a transmission-geometry sample cell for use in long-duration synchrotron X-ray powder diffraction studies of in situ mineral precipitation from aqueous ice–brine systems are presented in a recent article in Journal of Applied Crystallography [Thompson et al. (2018). J. Appl. Cryst. 51, 1197-1210]. The cell is capable of very slow cooling rates (e.g. 0.3 °C per day or less), and its performance is demonstrated with the results from a year-long study of the precipitation of the hydrated magnesium sulfate phase meridianiite (MgSO4·11H2O) from the MgSO4–H2O system. Evidence from the Mars Rover mission suggests that this hydrated phase is widespread on the present-day surface of Mars. However, as well as the predicted hexagonal ice and meridianiite phases, an additional hydrated sulfate phase and a disordered phase are observed.

Cold-cell experiments will produce the first in situ observations of mineral formation in freezing aquatic environments that are characteristic of oceans on Earth and other planetary objects. Such novel results will contribute to our understanding of the global processes that occur on, and shape, such bodies.

Posted 14 Aug 2018