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Solid state batteries can be built based on thiophosphate electrolytes such as beta-Li3PS4. For the preparation of these electrolytes, various solvent-based routes have been reported. For recycling of end-of-life solid state batteries based on such thiophosphates, we consider the development of dissolution and recrystallization strategies for the recovery of the model compound beta-Li3PS4. We show that recrystallization can only be performed in polar, slightly protic solvents such as N-methylformamide (NMF). The recrystallization is comprehensively studied, showing that it proceeds via an intermediate phase with composition Li3PS4*2NMF, which is structurally characterized. This phase has a high resistivity for the transport of lithium ions and must be removed in order to obtain a recrystallized product with a conductivity similar to the pristine material. Moreover, the recrystallization from solution results in an increase of the amorphous phase fraction next to crystalline beta-Li3PS4, which results in a decrease of the activation energy to 0.2 eV compared to 0.38 eV for the pristine phase.

The Jahn–Teller (JT) theorem constitutes one of the most fundamental concepts in chemistry. In transition‐element chemistry, the 3d4 and 3d9 configurations in octahedral complexes are particularly illustrative, where a distortion in local geometry is associated with a reduction of the electronic energy. However, there has been a lasting debate about the fact that the octahedra are found to exclusively elongate. In contrast, for Na9Bi5Os3O24, the octahedron around Os6+(5d2) is heavily compressed, lifting the degeneracy of the t2g set of 5d orbitals such that in the sense of a JT compression a diamagnetic ground state results. This effect is not forced by structural constraints, the structure offers sufficient space for osmium to shift the apical oxygen atoms to a standard distance. The relevance of these findings is far reaching, since they provide new insights in the hierarchy of perturbations defining ground states of open shell electronic systems., A Jahn–Teller‐compressed OsO6 octahedron resulting in an unprecedented large splitting of the t 2g levels and a diamagnetic ground state has been observed.

Crystals of Sc$_{2}$Si$_{2}$Te$_{6}$ have been grown and its crystal, micro- and electronic structures were investigated. The layered character of the title compound exhibits stacking faults that impede a full structural characterization by single crystal X-ray diffraction due to diffuse scattering. Based on high resolution transmission electron micrographs and diffraction patterns, the stacking faulted nature of the real structure of Sc$_{2}$Si$_{2}$Te$_{6}$ has been revealed. Different stacking models were derived from the idealized, faultless structure and the stacking disorder was quantitatively analyzed by Rietveld refinement of powder X-ray diffraction patterns. An energetic comparison of the stacking models by density functional theory is in line with the experimental observations. Further, the bonding situation was investigated by electronic structure calculations. Sc$_{2}$Si$_{2}$Te$_{6}$ is a narrow gap semiconductor with an indirect band gap of 0.65 eV.

The Jahn-Teller theorem constitutes one of the most popular and stringent concepts, applicable to all fields of chemistry. In open shell transition elements chemistry and physics, 3d4, 3d9, and 3d7(low-spin) configurations in octahedral complexes serve as particular illustrative and firm examples, where a striking change (distortion) in local geometry is associated to a substantial reduction of electronic energy. However, there has been a lasting debate, about the fact that the octahedra are found to exclusively elongate, (at least for eg electrons). Against this background, the title compound displays two marked features, (1) the octahedron of oxygen atoms around Os6+ (d2) is drastically compressed, in contrast to the standard JT expectations, and (2) the splitting of the t2g set induced by this compression is extreme, such that a diamagnetic ground state results. What we see is obviously a Jahn-Teller distortion resulting in a compression of the respective octahedron and acting on the t2g set of orbitals. Both these issues are unprecedented. Noteworthy, the splitting into a lower dxy (hosting two d electrons with opposite spin) and two higher dxz and dyz orbitals is so large that for the first time ever the Hund's coupling for t2g electrons is overcome. We show that these effects are not forced by structural frustration, the structure offers sufficient space for Os to shift the apical oxygen atoms to a standard distance. Local electronic effects appear to be responsible, instead. The relevance of these findings is far reaching, since they provide insights in the hierarchy of perturbations defining ground states of open shell electronic systems. The system studied here, offers substantially more structural and compositional degrees of freedom, such that a configuration could form that enables Os6+ to adopt its apparently genuine diamagnetic ground state., 8 pages, 6 figures + supplementary information (7 pages)

Crystal growth & design 20(8), 5346 - 5355 (2020). doi:10.1021/acs.cgd.0c00563, Dehydration of calcium acetate monohydrate (Ca(CH$_3$COO)$_2$·H$_2$O) by heating to 300 °C leads to the formation of anhydrous $α$-Ca(CH$_3$COO)$_2$. During heating and cooling cycles, high- and low-temperature forms of $α$-Ca(CH$_3$COO)$_2$ were discovered. The reversible first-order phase transformation between the two forms occurs in a temperature range between 150 and 170 °C. The crystal structures were solved from laboratory powder X-ray diffraction (PXRD) data. The low temperature form of $α$-calcium acetate (LT-$α$-Ca(CH$_3$COO)$_2$) crystallizes at room temperature in a primitive triclinic unit cell with space group $P1$ with lattice parameters of $a$ = 8.7168(3) Å, $b$ = 12.6408(3) Å, $c$ = 12.3084(3) Å, $α$ = 117.4363(17)°, $β$ = 77.827(2)°, $γ$ = 115.053(2)°, and a unit cell volume of 1090.23(6) Å$^3$. High-temperature $α$-calcium acetate (HT-$α$-Ca(CH$_3$COO)$_2$) crystallizes at 300 °C in a rhombohedral unit cell with space group $R^-3$, lattice parameters of $a$ = 21.1030(5) Å, $c$ = 8.7965(2) Å, and a unit cell volume of 3392.58(17) Å$^3$. In both crystal structures, edge sharing polyhedra of calcium cations and acetate anions that coordinate in both a mono- and bidentate way build up channel-like motifs. During the phase transition, the coordination mode of a bridging acetate anion changes from monodentate to bidentate, and the elliptical channels of the low temperature form become circular. This leads to both negative and positive thermal expansion along different principal axes in the crystal structure of LT-$α$-Ca(CH$_3$COO)$_2$ and to an overall considerably big volumetric thermal expansion., Published by ACS Publ., Washington, DC

Covalent organic frameworks (COFs) have emerged as a new class of molecularly precise, porous functional materials characterized by a broad structural and chemical versatility, leading to a diverse range of applications. Despite the increasing popularity of COFs, fundamental aspects of their formation are poorly understood and profound experimental insights into their formation processes are still lacking. Here we use a combination of in situ X-ray powder diffraction and Raman spectroscopy to elucidate the reaction mechanism of mechanochemically synthesized imine COFs, leading to the observation of key reaction intermediates. Real-time monitoring provides experimental evidence of templating effects by the liquid additive for the subsequent pore formation and layer assembly. Moreover, the solid-state catalyst scandium triflate Sc(OTf)3 is revealed to be instrumental in directing the reaction kinetics and mechanism, resulting in products with crystallinity and porosity en par with solvothermally synthesized COFs. This work highlights the potential of mechanochemistry as a green synthetic route towards COF synthesis, and emphasizes the subtle interplay between choice of liquid additives, catalysts, and activation procedure.

In the last decade, in situ powder X-ray diffraction (PXRD) monitoring of mechanochemical reactions has become a prominent technique for studying the course and mechanisms of organic and metal-organic solid formation [1]. Following our previous study on mechanochemical syntheses of metal-organic halogen-bonded cocrystals [2], in this work we have investigated mechanosynthesis of cocrystals containing CoCl2bzpy2 (bzpy = 2- benzoylpyridine) and a halogen bond donor, 1, 4- diiodotetrafluorobenzene (14tfib), by in situ PXRD. First, we performed experiments in solution, and have unexpectedly obtained three different products: two cocrystals with different metal- organic unit isomers, trans- (CoCl2bzpy2)(14tfib)2 and cis-(CoCl2bzpy2) (14tfib)2, and a cocrystal of 1:1 stoichiometry, cis-(CoCl2bzpy2)(14tfib). In order to determine whether single phases could be prepared, mechanosynthesis of obtained cocrystals was studied by in situ PXRD using synchrotron X- ray radiation. Three different liquid-assisted grinding experiments were monitored: grinding of CoCl2bzpy2 and 14tfib in the 1:2 molar ratio, one- pot grinding of CoCl2·6H2O, bzpy and 14tfib in the 1:2:2 molar ratio and grinding of CoCl2bzpy2 and 14tfib in the 1:1 molar ratio. All three monitored reactions revealed presence of a cocrystal with cis isomer as an intermediate and fast conversions to a final, thermodynamically more stable product, trans-(CoCl2bzpy2)(14tfib)2 , in less than 10 min. Single crystal X-ray diffraction experiments reveal that dominant supramolecular interactions in all obtained solids are I···Cl halogen bonds. In the trans- cocrystal halogen bonds form 2D networks while in cis- cocrystals 1D chains are formed. [1] T. Friščić et al., Nat. Chem., 2013, 5, 66. [2] K. Lisac and D. Cinčić, CrystEngComm., 2018, 20, 5955.

The isothermal compressibility of As2O5 has been studied up to a pressure of 19.5 GPa. High resolution X-ray powder diffraction and a membrane driven diamond anvil cell were used to determine the bulk moduli and their pressure derivatives according to various Equations of States and to investigate a potential ransformation to a high pressure polymorph. A mechanism which inhibits such a phase transformation up to the maximum applied pressure was revealed.

Journal of the American Chemical Society 143(9), 3430-3438 (2021). doi:10.1021/jacs.0c12249, Covalent organic frameworks have emerged as a powerful synthetic platform for installing and interconverting dedicated molecular functions on a crystalline polymeric backbone with atomic precision. Here, we present a novel strategy to directly access amine-linked covalent organic frameworks, which serve as a scaffold enabling pore-wall modification and linkage-interconversion by new synthetic methods based on Leuckart–Wallach reduction with formic acid and ammonium formate. Frameworks connected entirely by secondary amine linkages, mixed amine/imine bonds, and partially formylated amine linkages are obtained in a single step from imine-linked frameworks or directly from corresponding linkers in a one-pot crystallization-reduction approach. The new, 2D amine-linked covalent organic frameworks, rPI-3-COF, rTTI-COF, and rPy1P-COF, are obtained with high crystallinity and large surface areas. Secondary amines, installed as reactive sites on the pore wall, enable further postsynthetic functionalization to access tailored covalent organic frameworks, with increased hydrolytic stability, as potential heterogeneous catalysts., Published by American Chemical Society, Washington, DC

Crystal engineering has, so far, exclusively focused on the development of advanced materials based on small organic molecules. We demonstrate how the cocrystallization of a polymer significantly enhances its thermal stability without compromising its mechanical flexibility, while isomorphous replacement of one of the cocrystal components enables the formation of solid solutions with melting points that can be readily fine-tuned over a practically wide temperature range. The results of this study credibly extend the scope of crystal engineering and cocrystallization from small molecules to polymers.

Time-resolved mechanochemical cocrystallisation studies have so-far focused solely on neat and liquid-assisted grinding. Here, we report the monitoring of polymer-assisted grinding reactions using in situ X-ray powder diffraction, revealing that reaction rate is almost double compared to neat grinding and independent of the molecular weight and amount of used polymer additives.

CrystEngComm 24(12), 2305 - 2313 (2022). doi:10.1039/D2CE00162D, We demonstrate the ability to controllably desolvate a crystal-solvate system in a step-wise fashion through polymer-assisted grinding by varying the type and proportion of polymer agent used. A plausible mechanistic explanation is proposed based on a combination of experimental evidence and computational analysis. Specifically, Raman spectroscopy, total scattering pair distribution function analysis and computed reaction energies suggest that the desolvation process is associated with preferred interactions between the solvent molecules and specific polymers. This approach could potentially be extended to any type of material, including heat-sensitive materials, where classical desolvation by thermal processes is not possible, and provides an additional route for formulation processing., Published by RSC, London

X-ray powder diffraction is a well-established technique to analyse structural and microstructural properties of materials. The possibility to record in-situ powder diffraction data allows studying changes within the structure and microstructure of a sample that occur in dependence on the applied external conditions (e.g. temperature, pressure). In the present thesis, in-situ X-ray powder diffraction was used to study structural and microstructural changes of different samples occurring at elevated temperature or upon UV illumination. Several structural phase transitions were studied using the approach of parametric Rietveld refinement. In parametric Rietveld refinement a set of powder diffraction pattern is refined simultaneously, constraining the evolution of some parameters using mathematical models, so that only the variables of the model need to be refined. In order to model and analyse the behaviour of structural parameters, Landau theory and its corresponding equations were used, owing to the fact that structural parameters (e.g. lattice strain, changes in atomic positions or occupancy) comprise an order parameter as defined in Landau theory. For description of the crystal structure of materials, several different approaches were tested, e.g. atomic coordinates, symmetry modes, rigid body rotations or rigid body symmetry modes. The dependence of preparation conditions on the properties of nanomaterials and their growth kinetics was studied using Whole Powder Pattern Modelling. This method allows modelling X-ray powder diffraction pattern using the microstructure of the sample without the use of arbitrary profile functions. The Fourier transforms of frequently observed effects as crystallite shape and size distribution or density of various defects, like dislocations and stacking faults, are utilised in order to get the resulting diffraction profile. Two different systems with industrial application, CeO2 and Cu2ZnSnS4, which were produced using a sol-gel approach, were investigated., Pulverröntgenbeugung ist eine gängige Technik um strukturelle und mikrostrukturelle Eigenschaften von Materialen zu charakterisieren. Die Abhängigkeit dieser Eigenschaften von den Umgebungsbedingungen (wie z. B. Temperatur oder Druck) kann mittels in-situ Pulverröntgenbeugung untersucht werden. In der vorliegenden Arbeit wurde in-situ Pulverröntgenbeugung dazu verwendet, die strukturellen sowie mikrostrukturellen Veränderungen verschiedener Materialien, die bei erhöhten Temperaturen oder unter Einwirkung von UV-Licht auftreten, zu untersuchen. Mehrere strukturelle Phasenumwandlungen wurden mit Hilfe von parametrischer Rietveldverfeinerung analysiert. Die parametrische Rietveldverfeierung verfeinert einen Satz von Pulverröntgendaten simultan, wobei der Verlauf mancher Parameter durch mathematische Modelle gegeben ist, so dass, statt der einzelnen Parameterwerte, nur die Parameter des Modells bestimmt werden müssen. Um das Verhalten von Parametern der Kristallstruktur über einen Phasenübergang hinweg zu untersuchen und interpretieren, wurde die Landautheorie sowie die damit verbundenen Gleichungen verwendet, da strukturelle Eigenschaften (wie Gitterspannungen oder Änderungen in Atomposition- oder besetzung) einen Ordnungsparameter nach Landau darstellen. Mehrere verschiedene Ansätze wurden zur Beschreibung der Kristallstruktur des untersuchten Materials verwendet, wie traditionelle Atomkoordinaten, Symmetriemoden, Rotationen fester Atomgruppen und Symmetriemoden angewendet auf Atomgruppen. Whole Powder Pattern Modelling wurde dazu verwendet, den Einfluss der Herstellungsbedingungen auf Nanomaterialien und ihr Wachstum zu untersuchen. Whole Powder Pattern Modelling modelliert Röntgenbeugungsdaten mit Hilfe der Mikrostruktur des untersuchten Materials ohne willkürlich gewählte Profilfunktionen zu verwenden. Stattdessen werden beobachtbare Effekte, wie die Form und Größenverteilung der kristallinen Domänen oder ihre Defektdichte (z.B. durch Versetzungen oder Stapelfehler) genützt. Für die vorliegende Arbeit wurden Untersuchungen an zwei Materialien mit (potentieller) industrieller Anwendung, CeO2 und Cu2ZnSnS4, durchgeführt. Die Materialsynthese erfolgte mittels Sol-Gel-Methoden.

Due to the reduced informational content of powder diffraction data in comparison with single crystal diffraction, the challenge of increasing the accuracy in powder diffraction is of utmost importance. Several different ways of increasing accuracy in powder diffraction were investigated in the presented PhD thesis: possibilities and limitations of the maximum entropy method (MEM) for increasing accuracy of the electron density determination from high-resolution laboratory and synchrotron powder X-ray diffraction data, application of parametric refinement for the analysis of different models of coupling between strain and order parameter during structural phase transitions, and investigation of noble gas adsorption in MOFs by state of art laboratory and synchrotron powder diffraction., Auf Grund des reduzierten Informationsgehalts von Pulverbeugungsdaten im Vergleich mit der Einkristallbeugung, ist es von größter Wichtigkeit, die Genauigkeit der Pulverbeugung zu erhöhen. Im Zuge dieser Doktorarbeit wurden deshalb verschiedene Möglichkeiten untersucht, wie die Genauigkeit in der Pulverbeugung erhöht werden kann: Untersuchung der Möglichkeiten und Grenzen der Methode der Maximalen Entropie (MEM) mit welcher die Elektronendichte präzise aus hochauflösenden Labor- und Synchrotron-Röntgenpulverbeugungsdaten bestimmt werden kann; Anwendung der parametrisierten Verfeinerung um verschiedene Modelle der Kopplung zwischen Strain und Ordnungsparameter während eines strukturellen Phasenübergangs zu analysieren und Untersuchungen von Edelgasabsorption in MOFs mittels fortgeschrittener Labor- und Synchrotron-Pulverbeugung.

X-ray powder diffraction is as a powerful tool for structural analysis of crystalline compounds which do not grow as single crystals, but a polycrystalline bulk. When applied under non-ambient conditions, or when data are collected at consecutive time intervals, X-ray powder diffraction can be readily turned into a valuable method for in situ following, visualizing and ultimately explaining a number of solid state processes and chemical reaction. In the scope of my PhD work, an attempt to demonstrate the power and applicability of in situ X-ray powder diffraction in studying the reactivity of the solid state was made. In a period of almost 3 years, various systems were investigated when submitted under different external stimuli to initiate specific process and/or reaction in the solid state. The results described in this thesis were done working on six (independent) research projects, presented herein as separate case studies. (It should be noted that in parallel to the work performed on these six projects, research was done in several other topics, part of which is already published in scientific journals and the references are given in CV, attached at the end of the thesis)., Die Röntgenpulverdiffraktion ist ein mächtiges Werkzeug zur strukturellen Analyse von kristallinen Verbindungen, welche nicht als Einkristalle, dafür aber als pulverförmiges Material vorliegen. Werden Pulverröntgendiffraktionsdaten unter Nicht-Umgebungsbedingungen oder in nacheinander folgenden Zeitintervallen aufgenommen, so zeigt sich die Bedeutsamkeit der Methode, um Festkörperprozesse und chemische Reaktionen in-situ zu verfolgen, sie zu visualisieren und eine wissenschaftliche Erklärung zu finden. Im Rahmen der vorliegenden Doktorthesis wurde ein Versuch unternommen, die Mächtigkeit und Anwendbarkeit der in-situ Pulverröntgendiffraktion anhand der Untersuchung der Reaktivität von Festkörpern zu demonstrieren. In einem Zeitraum von beinahe drei Jahren wurden verschiedene Systeme unterschiedlichst extern angeregt, um spezifische Prozesse und/oder Reaktionen in Festkörpern auszulösen. Die Ergebnisse, die in der vorliegenden Arbeit beschrieben werden, rühren von sechs (unabhängigen) Forschungsprojekten her, wobei diese hier in separaten Fallstudien beschrieben werden. (Nebenbei muss bemerkt werden, dass parallel zu den sechs beschriebenen Forschungsprojekten, Forschung auf verschiedenen anderen Themen durchgeführt wurde, welche teilweise bereits in wissenschaftlichen Zeitschriften publiziert wurden. Die Referenzen dazu sind im Lebenslauf am Ende der Arbeit gelistet.)

X-ray powder diffraction is a well-established technique to analyse structural and microstructural properties of materials. The possibility to record in-situ powder diffraction data allows studying changes within the structure and microstructure of a sample that occur in dependence on the applied external conditions (e.g. temperature, pressure). In the present thesis, in-situ X-ray powder diffraction was used to study structural and microstructural changes of different samples occurring at elevated temperature or upon UV illumination. Several structural phase transitions were studied using the approach of parametric Rietveld refinement. In parametric Rietveld refinement a set of powder diffraction pattern is refined simultaneously, constraining the evolution of some parameters using mathematical models, so that only the variables of the model need to be refined. In order to model and analyse the behaviour of structural parameters, Landau theory and its corresponding equations were used, owing to the fact that structural parameters (e.g. lattice strain, changes in atomic positions or occupancy) comprise an order parameter as defined in Landau theory. For description of the crystal structure of materials, several different approaches were tested, e.g. atomic coordinates, symmetry modes, rigid body rotations or rigid body symmetry modes. The dependence of preparation conditions on the properties of nanomaterials and their growth kinetics was studied using Whole Powder Pattern Modelling. This method allows modelling X-ray powder diffraction pattern using the microstructure of the sample without the use of arbitrary profile functions. The Fourier transforms of frequently observed effects as crystallite shape and size distribution or density of various defects, like dislocations and stacking faults, are utilised in order to get the resulting diffraction profile. Two different systems with industrial application, CeO2 and Cu2ZnSnS4, which were produced using a sol-gel approach, were investigated., Pulverröntgenbeugung ist eine gängige Technik um strukturelle und mikrostrukturelle Eigenschaften von Materialen zu charakterisieren. Die Abhängigkeit dieser Eigenschaften von den Umgebungsbedingungen (wie z. B. Temperatur oder Druck) kann mittels in-situ Pulverröntgenbeugung untersucht werden. In der vorliegenden Arbeit wurde in-situ Pulverröntgenbeugung dazu verwendet, die strukturellen sowie mikrostrukturellen Veränderungen verschiedener Materialien, die bei erhöhten Temperaturen oder unter Einwirkung von UV-Licht auftreten, zu untersuchen. Mehrere strukturelle Phasenumwandlungen wurden mit Hilfe von parametrischer Rietveldverfeinerung analysiert. Die parametrische Rietveldverfeierung verfeinert einen Satz von Pulverröntgendaten simultan, wobei der Verlauf mancher Parameter durch mathematische Modelle gegeben ist, so dass, statt der einzelnen Parameterwerte, nur die Parameter des Modells bestimmt werden müssen. Um das Verhalten von Parametern der Kristallstruktur über einen Phasenübergang hinweg zu untersuchen und interpretieren, wurde die Landautheorie sowie die damit verbundenen Gleichungen verwendet, da strukturelle Eigenschaften (wie Gitterspannungen oder Änderungen in Atomposition- oder besetzung) einen Ordnungsparameter nach Landau darstellen. Mehrere verschiedene Ansätze wurden zur Beschreibung der Kristallstruktur des untersuchten Materials verwendet, wie traditionelle Atomkoordinaten, Symmetriemoden, Rotationen fester Atomgruppen und Symmetriemoden angewendet auf Atomgruppen. Whole Powder Pattern Modelling wurde dazu verwendet, den Einfluss der Herstellungsbedingungen auf Nanomaterialien und ihr Wachstum zu untersuchen. Whole Powder Pattern Modelling modelliert Röntgenbeugungsdaten mit Hilfe der Mikrostruktur des untersuchten Materials ohne willkürlich gewählte Profilfunktionen zu verwenden. Stattdessen werden beobachtbare Effekte, wie die Form und Größenverteilung der kristallinen Domänen oder ihre Defektdichte (z.B. durch Versetzungen oder Stapelfehler) genützt. Für die vorliegende Arbeit wurden Untersuchungen an zwei Materialien mit (potentieller) industrieller Anwendung, CeO2 und Cu2ZnSnS4, durchgeführt. Die Materialsynthese erfolgte mittels Sol-Gel-Methoden.

The combination two-dimensional detectors, powder diffraction and synchrotron light sources has been staggeringly successful, opening doors to many new experiments. The great advantages of such data collection lie in the short exposure times as well as in the huge redundancy. A large angular region of the Bragg cone is recorded in a single exposure; indeed most detectors are set up perpendicular and centrally to the primary beam, intercepting the Bragg cone over the entire azimuthal range. The standard practice is to integrate the image along the ellipses described by the intersection of the cone with the planar detector to a conventional powder pattern. This commonly reduces the amount of information by the square root of the number of pixels. Does this represent the gamut of information contained in a powder diffraction image? A glance at an image from a calibration standard might lend itself to such a conclusion. Less perfect samples, as well as sample environments leave distinctive artefacts on images. How can they be extracted, filtered or interpreted? Methods offering answers to these questions are introduced. The origins of powder diffraction were based on diffraction images, however with the onset of equatorial electronic point detectors all high quality powder diffraction experiments switched to this method. It has remained the experimental doctrine to this day. Only recently have powder diffraction scientists rediscovered the allure of diffraction images. Indeed high pressure powder diffraction experiments are unthinkable without two-dimensional detectors. What seems like such a positive development does, on closer inspection have its problems. Two dimensional correction factors effectively do not exist for powder diffraction experiments. All commonly used Lorentz and polarization (LP) corrections are meaningless outside the thin equatorial strip for which they were determined. Furthermore various other detector and geometry dependent factors have to be considered should a high quality powder diffraction pattern be extracted from the image. The first chapter of this thesis takes on this challenge and presents all applicable two-dimensional correction factors, as well as the basis for their application: the experimental set-up. Determining the geometry to the highest possible precision is paramount to the quality of the experiment. How can one achieve this goal, without losing oneself in diverging refinements and renitent analysis software? Pattern recognition methods and whole image refinement have been used to solve the two main problems of calibration and are presented in the second chapter. The first global search gives sensible starting values for what is probably the most extreme refinement single pattern powder diffraction has to offer: whole image refinement. Here the entire two-dimensional image is rebuilt, based on the initial values, and subtracted from the experimental image. This residual is then minimized using a Levenberg-Marquardt non-linear least squares refinement algorithm. This method leads to calibrations that are at least one order of magnitude more precise than traditional calibration routines. This is of fundamental importance for the effective use of future high resolution area detectors. A perfect calibration does not suffice to ensure a successful data reduction. Especially in situ experiments - the forte of two-dimensional detectors cause intensity aberrations that need to be removed before the image can successfully be integrated to a conventional powder diffractogram. The source of deviations can be sorted into two camps: those originating from the sample environment and those emanating from the sample itself. Of course the former is both more easily recognized visually and also removed more simply by the fractile filters presented in the third chapter. When intensity deviations originate from the sample the matter becomes far more complex. A new distribution function, the normal Pareto function, has been shown to describe the intensity distribution that results from small sample amounts without substantial sample rotation, as is the case in high pressure powder diffraction. The great benefit of this function is that it opens the possibility of extracting a fractional filtering setting which ultimately leads to normally distributed intensities. Structural analysis from diffraction data is always connected to a plethora of reliability values, describing the raw data as well as the refinement quality. Powder diffraction images completely lack any numerical estimation of their quality. Functions giving universally comparable, detector independent reliability values for images can be found in chapter four., Die Kombination von Pulverdiffraktometrie, großen Flächendetektoren und Synchrotronquellen ist phänomenal erfolgreich und ermöglicht viele neue Experimente. Die großen Vorteile solcher Datengewinnung liegen in den kurzen Belichtungszeiten sowie in der enormen Redundanz. Ein großer Winkelbereich des Brechungskegels wird in einer einzigen Belichtung erfasst, häufig wird sogar der gesamte Kegelschnitt detektiert, da die meisten Kameras rechtwinklig und mittig zum Primärstrahl positioniert sind. Es ist dann gebräuchlich, die gesamten Ellipsen, die die Kegelschnitte beschreiben, zu einem konventionellen Pulverdiffraktogramm zu integrieren. Üblicherweise wird die Datenmenge um eine Quadratwurzel der Anzahl der Pixel reduziert. Gibt dieses jedoch die komplette Information aus dem Streuungsbild zufrieden stellend wieder? Ein Blick auf ein ideales Kalibrierungsbild könnte einen solchen Schluss nahe legen. Minder perfekte Proben sowie Effekte von Probenumgebungen hinterlassen jedoch starke Spuren auf den Bildern. Hier liegt das Problem: Wie können auch solche Daten gefiltert und interpretiert werden? In dieser Arbeit werden Methoden vorgestellt, die darüber Aufschluss geben und die Ergebnisse von verblüffender Qualität ermöglichen. Ursprünglich basierte die Pulverdiffraktometrie auf Streubilder. Mit der Ankunft der äquatorialen Punktzählrohren übernahm diese Methode die Messherrschaft über qualitativ hochwertige Pulverdiffraktogramme. Bis heute setzt sich diese experimentelle Doktrin durch. Kürzlich haben Wissenschaftler aber die Vorzüge der Streubilder wiederentdeckt. So ist beispielsweise die gesamte Hochdruckpulverdiffraktometrie ohne den Einsatz von großen zweidimensionalen Detektoren undenkbar. Was auf dem ersten Blick als Segen daherkommt, bringt allerdings auch einige Probleme mit sich. Es existieren effektiv kaum zweidimensionale Korrekturfunktionen für die Pulverdiffraktometrie. Alle gebräuchlichen Lorentz und Polarisationskorrekturen (LP) sind außerhalb des dünnen äquatorialen Bereichs, für den sie entwickelt wurden bedeutungslos. Weiterhin müssen viele geometrische und detektorische Eigenschaften in die Korrekturen einfließen, um ein qualitativ hochwertiges Pulverdiffraktogramm aus dem Bild zu extrahieren. Diesem Problem nimmt sich das erste Kapitel dieser Arbeit an: Es stellt alle nötigen Korrekturfunktionen dar, zusammen mit ihrer Basis: der geometrischen Beschreibung des experimentellen Aufbaus. Die Bestimmung aller geometrischen Parameter zur höchstmöglichen Präzision ist bedeutsam für die Qualität des Experiments. Wie erreicht man dieses Ziel, ohne sich in den Wirren divergierender Verfeinerungen und Analysesoftware zu verlieren? Hier werden Methoden der Mustererkennung und das so genannte ‚whole image refinement‘ also die Komplettbildverfeinerung eingesetzt um die beiden Hauptprobleme der Kalibrierung zu lösen. Methode eins, die Mustererkennung, ist eine globale Optimierung, gibt vernünftige Startwerte für die zweite Methode, eine lokale Optimierung der Parameter durch ‚whole image refinement‘. Hier wird das gesamte zwei-dimensionale Bild basierend auf den Startwerten und den Probeneigenschaften berechnet und vom experimentellen Bild abgezogen. Die Differenz wird gewichtet und stellt für den Minimierungsalgorithmus den zu reduzierenden Kostenfaktor dar. Diese Methode führt zu Kalibrierungen, die mindestens eine Größenordnung genauer sind, als solche die man mittels traditioneller Methoden errechnet. Dieses ist für die effektive Nutzung zukünftiger hoch auflösender Detektoren von fundamentaler Bedeutung. Eine perfekte Kalibrierung reicht allerdings nur in der seltensten Fällen für eine gelungene Integration. Gerade in situ Experimente welche die Stärke der zwei-dimensionalen Detektoren sind verursachen stark abweichende Intensitäten. Diese lassen sich nach Ihrem Ursprung unterscheiden: Entweder sie stammen von der Probenumgebung oder von der Probe. Natürlich sind die ersteren leichter mit dem Auge zu erkennen und auch leicht mit Filter zu entfernen die in Kapitel drei vorgestellt werden. Schwieriger gestaltet es sich bei den letzteren. Eine neue Verteilungsfunktion, die normale Pareto Verteilung, beschreibt die Intensitätsverteilung von kleinen Probenmengen, die kaum im Strahl rotiert werden. Diese Verhältnisse werden gerade bei Hochdruckuntersuchungen realisiert. Der große Vorteil dieser Beschreibung ist: Sie eröffnet die Möglichkeit, vernünftige Filtereinstellungen zu berechnen, die dann eine normale Verteilung wieder herstellen können. Strukturanalysen werden immer von einer Vielzahl von R-(reliability) Werten begleitet, die die Rohdatenqualität sowie die Verfeinerungsqualität bewerten. Pulverstreuungsbilder sind in dieser Beziehung bisher leer ausgegangen. In Kapitel vier werden Funktionen für universell vergleichbare, Detektor unabhängige R-Werte vorgestellt.