The Inorganic Crystal Structure Database (ICSD) is the world's largest database of fully evaluated and published crystal structure data, mostly obtained from experimental results. However, the purely experimental approach is no longer the only route to discover new compounds and structures. In the past few decades, numerous computational methods for simulating and predicting structures of inorganic solids have emerged, creating large numbers of theoretical crystal data. In order to take account of these new developments the scope of the ICSD was extended in 2017 to include theoretical structures which are published in peer-reviewed journals. Each theoretical structure has been carefully evaluated, and the resulting CIF has been extended and standardized. Furthermore, a first classification of theoretical data in the ICSD is presented, including additional categories used for comparison of experimental and theoretical information.

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This study covers the experimentally observed modifications of AlN, investigates their relations and searches for new possible modifications combining data mining and ab initio methods.

Zinc oxide is one of the most investigated compounds in materials science, both experimentally and theoretically, while in nature it appears only rarely, as the mineral zincite. Yet there are still many open questions: Is it still possible to observe or synthesize new modifications of zinc oxide? And can we improve the properties of a material that has already been investigated in thousands of studies? What is the connection between zincite, zinc sulfide and zinc oxide, and can we finally explain the controversial mineral matraite? In short, Yes: the answer to these questions is polytypism. We identify a multitude of possible stable polytypes for zinc oxide, and we show that by varying the stacking order, we can finetune the electronic properties such as the direct primary and secondary band gaps in zinc oxide without adding dopant atoms. Fig. 1 Visualization of the experimentally observed (a and b) and calculated (c-i) modifications of zinc oxide: (a) wurtzite (2H) type; (b) sphalerite (3C) type; (c) 4H polytype; (d) 5H polytype; (e) 6H polytype; (f) 8H polytype; (g) 9R polytype; (h) 12R polytype; (i) 15R polytype.This journal is

We report on a combined ultra-fast in situ SAXS and WAXS study along a free-jet providing insight into the evolution of the morphology and crystalline structure of CdS quantum dots in the very early stage of nucleation between 100 µs and 2.5 ms with a time resolution down to 10 µs. Accessing this yet unexplored time regime provides direct evidence of a two-step mechanism via formation of prenucleation clusters followed by nanoparticle nucleation from coalescing precursors. Using ab initio calculations, the latter species is identified as Cd 13 S 4 (SH) 18 clusters, the stability of which results from a compact surface and inner structure.