Challenges in the structural science of materials

Abstract

The articles published recently in IUCrJ continue to exemplify the developments and challenges in the structural science of materials. They illustrate the exciting rapid developments in technique, sources, instrumentation and data analysis, the continuing role and growing power of computation in the field, and the increasing ability to investigate complex structural problems in materials that are of direct relevance to their function.Advances in technique and data analysis are well illustrated by the review article of Van Aert et al. (2016) which describes how developments in transmission electron microscopy coupled with novel data analysis methods can give accurate structural information on nanostructured and disordered materials; and illustrates how increased precision can be achieved in atomic positions using these techniques. Several examples illustrate the power of the approach, for example the accurate information on atomic coordinates adjacent to a twin boundary in CaTiO 3 , as illustrated in Fig. 1.Significant developments in techniques are also described in the article of Rius et al. (2015), who describe how the synchrotron-based through-the-substrate X-ray microdiffraction technique (tts-XRD) can now be used to obtain structural information on microvolumes of crystals embedded in a complex matrix -a development of importance for several areas of materials science including the study of complex mineralogical samples. The use of synchrotron radiation in operando methods in structural science, particularly relating to catalytic systems, continues to grow as illustrated by the recent study of Lezcano-Gonzá lez et al. (2016) who investigated complex structural changes during the operation of a microporous dehydroaromatization catalyst.A core area of crystallography is of course the determination and modelling of electron density, recent developments in which are discussed in the article of Macchi et al. (2015), who emphasize multi-technique approaches, and show the importance of developments in sources and detectors and of new multipole models for describing charge densities accurately. Related topics are considered in the article of Sanjuan-Szklarz et al. (2016), which discusses how improved accuracy may be obtained by using transferable aspherical atom models (TAAM) in structure refinements and how such an approach can yield highquality structures even from low-resolution data.