STOE USER TALK: STRUCTURE SOLUTION FROM POWDER DIFFRACTION DATA

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Polyoxometallates are known to form a plethora of large polyanions, the number of which even grows with the introduction of heteroatoms. They are frequently synthesized under solvothermal conditions, but with suitable precursors even at room temperature reactions can be carried out. Under such conditions the growth of single crystals is not always possible and structure solution from powder diffraction data remains the only way to determine the crystal structure. Herein, the challenging case of the arsenato polyoxovanadate [Ni(en)3]2[V12As8O40(H2O)]x4H2O is presented, where both lab and synchrotron based powder diffraction data were employed for structure solution and refinement.

35 min.

STOE USER TALK: How to Benefit from Systematic Errors

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The extraction of valuable information from systematic errors is the key to progress in crystallography as they
convey not only errors in the structure model, but also methodological problems in data acquisition and data processing protocols, in protocols of data quality evaluation itself, in models of diffraction, extinction, absorption
etc., as well as in software for hardware like detectors. Concrete examples are given to demonstrate what data quality evaluation as developed by DataQ Intelligence 
is capable of doing even without knowing all the technical details.

57 min.

STOE USER TALK: STRUCTURE DETERMINATION OF [NH4][SeCN] AND ITS REACTIVITY TOWARDS Ag[SeCN]

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About 200 years ago, ammonium cyanate, [NH4][OCN], was obtained by Liebig and Wöhler as a fluffy, white powder from the reaction of dry ammonia with cyanic acid. They also noticed its rearrangement at room temperature into urea, [NH2]2CO, a compound which has the same sum formula as ammonium cyanate.[1,2] From this the concept of isomerism was deduced and remains unchanged until today […]

26 min.

STOE USER TALK: OVERWEIGHT AND DIM LIT: X-RAY DIFFRACTION BECOMING CHALLENGED BY PD DR. CONSTANTIN HOCH, LMU MUNICH

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Absorption correction is today a highly automated process performed in the course of data reduction, on most diffractometer software suites directly after the measurement. In the utmost cases, this process is not handled with the required care, and by this considerable systematic errors can be introduced into the data sets. The impacts of missing or wrong absorption corrections are subtile but inflict all structure parameters, from standard deviations of atomic parameters and residual electron densities to R values. It is of high importance to rationalise functionality and methods of absorption correction in order to avoid systematic errors. A brief overview is given on the theoretical background and different methods of absorption correction algorithms. Some examples from our research on amalgams showing unusually high absorption effects are given to illustrate problems of absorption and how to overcome them.

54 min.

USER TALK: COMPLEXITY IN STRUCTURES DRIVEN BY ION DYNAMICS

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Solid ion conductors are fascinating materials for energy conversion and storage applications. Due to their intrinsic properties and especially their high ion mobility in the lattice they are often characterized by complex crystal structures, polymorphism and the loss symmetry during structural phase transitions. This last aspect often causes twinning and demands the collection of precise data and the usage of group-subgroups relations to solve and understand their crystal structures. Beside the structural features of a selection of solid ion conductors discussed in this presentation also intriguing electronic property changes can occur that are closely related to the ion dynamics and structure changes upon heating or cooling of such materials. In this talk we present a series of copper and silver ion conductors that also show reasonable electronic conductivities which characterize them as mixed-conducting semiconductors. […]

55 min.

THE STOE SPHERES – A NEW ANALYTICAL TOOL

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STOE SPHERES, a new analytical tool for:
Visualization of direction-dependent populations
Easy assessment of coverage for desired direction-dependent scaling
Representation of direction-dependent deviations, changes and scale factors
Recognition of direction-dependent underscaling/overscaling
Better understanding of Spherical Harmonics
Identification of outliers
Join us for this presentation followed by a live-demonstration of the new features!

Featuring Friedemann Hahn, STOE.

56 min.

PUSHING THE LIMITS – STOE’S TWIN PORT METALJET SOLUTION

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See how we designed for Karlsruhe Institute of Technology an X-ray diffraction system for both, single-crystal diffraction and powder diffraction powered by a dual port Excillum MetalJet source. With two exchangeable wavelengths usable for both end-stations, a unique service and alignment concept and the latest Dectris detector technique, this system tackles their most demanding applications.