Ab Initio Structure Determination of Vaterite by Automated Electron Diffraction

tion that is fundamental for understanding material properties. Still, a number of compounds have eluded such kinds of analysis because they are nanocrystalline, highly disordered, with strong pseudosymmetries or available only in small amounts in polyphasic or polymorphic systems. These materials are crystallographically intractable with conventional Xray or synchrotron radiation diffraction techniques. Single nanoparticles can be visualized by high-resolution transmission electron microscopy (HR-TEM) up to sub�ngstrom resolution, [2] but obtaining 3D information is still a difficult task, especially for highly beam-sensitive materials and crystal structures with long cell parameters. Elec…

Corrosion of Heritage Objects: Collagen‐Like Triple Helix Found in the Calcium Acetate Hemihydrate Crystal Structure

Abstract Helical motifs are common in nature, for example, the DNA double or the collagen triple helix. In the latter proteins, the helical motif originates from glycine, the smallest amino acid, whose molecular confirmation is closely related to acetic acid. The combination of acetic acid with calcium and water, which are also omnipresent in nature, materializing as calcium acetate hemihydrate, was now revealed to exhibit a collagen‐like triple helix structure. This calcium salt is observed as efflorescence phase on calcareous heritage objects, like historic Mollusca shells, pottery or marble reliefs. In a model experiment pure calcium acetate hemihydrate was crystallized on the surface of…

Ab-initio-Strukturbestimmung von Vaterit mit automatischer Beugungstomographie

A hydrated crystalline calcium carbonate phase: Calcium carbonate hemihydrate.

Hydrous CaCO 3 gets a new structure Calcium carbonate (CaCO 3 ) forms important minerals on Earth and is a model system for understanding crystal nucleation. Three different structures of CaCO 3 are known, along with two structures that are hydrated. Zou et al. found a third hydrated CaCO 3 structure formed from amorphous CaCO 3 in the presence of magnesium ions. The discovery illustrates the importance of amorphous precursors for producing new materials. Science , this issue p. 396

Korrosion von Kulturgut: Entdeckung einer kollagenartigen Tripelhelix in der Kristallstruktur von Calciumacetat‐Hemihydrat

CCDC 1429729: Experimental Crystal Structure Determination

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CCDC 1429728: Experimental Crystal Structure Determination

Related Article: Enrico Mugnaioli, Iryna Andrusenko, Timo Schüler, Niklas Loges, Robert E. Dinnebier, Martin Panthöfer, Wolfgang Tremel, Ute Kolb|2012|Angew.Chem.,Int.Ed.|51|7041|doi:10.1002/anie.201200845

CCDC 1958904: Experimental Crystal Structure Determination

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