Thèses sur le sujet « X-ray crystal and powder diffraction »
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1
McBride, Lorraine. « Determination of organic crystal structures by X ray powder diffraction ». Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248694.
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Chan, Fung Choy. « Powder X-ray diffraction studies of structural and kinetic aspects of polymorphism ». Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327050.
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Aziz, Fauziah Haji. « Indexing and structural studies of materials by high-resolution X-ray powder diffraction ». Thesis, University of Surrey, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.232903.
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Docherty, Andrea. « Crystal structure solution and refinement of pharmaceutical molecules using x-ray powder diffraction ». Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399726.
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Rodriguez, Asiloe Jasmina Mora. « High resolution powder diffraction studies of molecular solids ». Thesis, Keele University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321299.
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Smith, Elaine D. L. « Combined molecular modelling and powder X-ray diffraction for crystal structure solution of organic materials ». Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/249.
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Tsuboi, Chiaki. « X-ray crystal structure analyses of magnetically oriented microcrystalline suspensions ». Kyoto University, 2016. http://hdl.handle.net/2433/216190.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第19936号
農博第2186号
新制||農||1044(附属図書館)
学位論文||H28||N5009(農学部図書室)
33022
京都大学大学院農学研究科森林科学専攻
(主査)教授 木村 恒久, 教授 西尾 嘉之, 教授 髙野 俊幸
学位規則第4条第1項該当
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Hou, Weimin. « A novel method for the determination of single crystal elastic constants using powder X-ray diffraction ». Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6338.
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The elastic properties of a material have long been a subject of interest in materials science and physics. Especially, a complete determination of the single crystal compliance and stiffness tensor is of great importance, as the single crystal elastic tensor provides a complete description of the elastic properties of a material. There are numerous materials that are only available in polycrystalline form. Many of these polycrystalline materials are of great interest, such as the polycrystalline materials synthesized under high pressure conditions, for which the elastic properties under high pressure conditions are particularly important. However, traditional methods to measure the elastic constants apply only to single crystals. Recently, Singh and co-workers have developed a method, using energy dispersive X-ray diffraction to measure the single crystal elastic constants of a material at elevated pressures, which, for the first time, enabled the single crystal elastic tensors of numerous polycrystalline samples to be determined. Inspired by the energy dispersive X-ray diffraction method, we have undertaken to develop a novel method, using angle dispersive X-ray diffraction techniques combined with a two-dimensional X-ray recording area detector, to measure the single crystal elastic constants of powder samples. We have obtained important results that will enable the single crystal elastic constants of concerned material to be determined from Debye rings recorded on the X-ray recording image plate. In comparison to the energy dispersive X-ray diffraction method, the angle dispersive X-ray diffraction method offers advantages, as we will demonstrate.
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Dall'Olio, Laura <1991>. « Survey of methodologies of pharmaceutical interest for quantification of crystal form via X-Ray Powder Diffraction ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9769/1/Dall%27Olio_Laura_Tesi.pdf.
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The interest on polymorphism of arises from their different properties. A strategy to improve the properties of compound, is the formation of cocrystal. In this PhD project, cocrystal statistical analysis and experimental screening of allantoin and some coformers were performed. No cocrystal was obtained, experimental results disagree with the statistical analysis.
Quantitative method of crystalline forms via X-Ray Powder Diffraction are extremely interesting for pharmaceutical companies. In the thesis real cases with different approaches of quantitative analysis are reported.
I presented the quantification of paracetamol form II impurity in Tachifludec containing paracetamol form I using univariate method in which the main issue is the identification of a specific peak. The presence of several peaks in the formulation was overcome by applying the standard addition method spiking the formulation with form II. Univariate and multivariate method NAS were compared, and the best results were obtained with the application of the multivariate method. These approaches were also evaluated in the case of mixture amorphous-crystalline. Furthermore, it was studied the potential use of stable amorphous surrogate instead to the unstable real amorphous. Even in these cases, multivariate method achieved the best results.
The novel quantification method Direct derivation (DD) based on intensity–composition equation was applied to determine crystallinity of mixture amorphous-crystalline. The quantification method was evaluated in three scenarios: method a) with unit cell parameters, method b) structural information is unknown, and method c) only the mixtures’ patterns are available. Method a and b achieved more accurate results because of better description of the crystalline phase. Method b was evaluated in sample covered by containment system as the Kapton® film to evaluate the analysis of highly potent compounds. The DD method has been revealed the best method to estimate the crystallinity degree of formulation containing highly potent compound deposited on catheter balloon.
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Vella-Zarb, Liana. « The complementary use of theoretical structure prediction and X-ray powder diffraction data in crystal structure determination ». Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/504/.
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The successful prediction of the crystal structure and symmetry of a material can give valuable insight into many of its properties, as well as the feasibility of thermodynamically stable poly-morphs to exist. It is not uncommon, however, for numerous theoretical structures to be found within a narrow energy range, making absolute characterisation of the crystal structure impossi-ble. The aim of this project was to investigate a number of structures from this scenario, high-lighting the key differences between three potential methods for the automated comparison of predicted and experimental crystal structures. This work was carried out by comparing the simulated powder diffraction patterns of theoretical predicted crystal structures of small organic materials with their experimental powder diffraction patterns, so that the experimentally identified structure could be automatically singled out from the many calculated. The use of traditional agreement factors (eg. Rwp) was compared with more sophisticated approaches namely PolySNAP, which uses principal-component analysis, and Compare.x, an algorithm based on weighted cross-correlation. Five structures were analysed, two of which had not been previously characterised. As the structure prediction calculations are carried out at 0K, and experimental data were collected over a range of temperatures (10K-293K), the effect of the resulting variations in lattice parameters on the automated processes is discussed. In all cases, Rwp has proven to be a poor and unreliable discriminator in the comparison of pre-dicted and experimental structures. The more contemporary methods based on PolySNAP and Compare.x both gave encouraging results when used to study the three known structures imida-zole, chlorothalonil and 5-azauracil, and they have consequently been used in the successful so-lution of the two previously unknown structures adenine and guanine. A difference in sensitivity in the matching of data collected at different temperatures between the latter approaches was noted. It was found that although there is considerable overlap between the two methods, they are not absolutely interchangeable, and this distinction may be exploited in future work where more case-specific comparisons are carried out. Automated comparison techniques cannot yet replace visual comparison completely, but they reduce it drastically. Ultimately, comparisons made computationally serve as a complement to human judgement, but they may not yet elimi-nate it.
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Chen, Hong. « Open-framework Structures Built by Inorganic Clusters : Synthesis and Characterization ». Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-106853.
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Novel open-framework germanates and vanadoborates, which are constructed from typical types of clusters, have been synthesized based on different strategies. The crystal structures are solved by using single crystal X-ray diffraction (SXRD) technique or by combined techniques. Additionally, the structures of two open-framework materials, PKU-3 and PKU-16, are determined from nano-sized crystals by rotation electron diffraction (RED) combined with powder X-ray diffraction (PXRD). This thesis serves as an introduction to synthesis of open-framework germanates and vanadoborates based on different design strategies. Two germanates are obtained; SU-74 is achieved by employing a novel structure directing agent (SDA), SUT-8 is achieved by assembling the novel structure building units (SBUs) of Co@Ge14 with the introduction of cobalt ions in the synthesis. Four strategies are successfully used in construction of open-framework vanadoborates: using metal-oxo polyhedra as the linkages in SUT-6; applying the scale chemistry approach in SUT-7; employing metal-organic complexes as the linkages in SUT-12, SUT-13, SUT-14; and introducing covalent bond organic linkages into SUT-10 and SUT-11. Single crystal X-ray diffraction is used to conduct the structure determination in combination with other techniques. Furthermore, the structures of two open-framework materials, an aluminoborate PKU-3 and a germanosilicate PKU-16, are solved from nano-sized crystals using RED data. The structures are further confirmed by Rietveld refinement against PXRD data. The advantages of the RED techniques are demonstrated in two aspects. In PKU-3, the presence of seriously preferred orientation and light elements in the structure makes it difficult for structure determination by PXRD, but it is easier by RED. In PKU-16, the RED technique is used to determine its structure from the as-synthesized multi-phasic sample containing nano-sized crystals. After the structure of PKU-16 has been solved, the synthesis of this interesting phase can be optimized and pure PKU-16 can be obtained. Keywords: Open-framework, germanates, vanadoborates, aluminoborates, germanosilicates, crystal structure, hydrothermal synthesis, single crystal X-ray diffraction, rotation electron diffraction, powder X-ray diffraction
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Muroyama, Norihiro. « Studies of inorganic crystal structures and gas adsorption process in mesoporous crystals : new approach through analysis of electron charge distribution by synchrotron powder X-ray diffraction / ». Stockholm : Department of Physical, Inorganic and Structural Chemistry, Stockholm university, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7367.
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Höglin, Viktor. « Structure-Magnetic Relationships in the Fe-Mn-P-Si System for Energy Applications ». Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-234516.
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Demands for new, energy-efficient appliances have greatly increased in response to our growing need for a more environmentally friendly society. Magnetic refrigeration is a technique that utilizes the magnetocaloric effect, with possible energy savings of up to 30% compared to commercial gas compression refrigerators. A material appropriate for commercial magnetocaloric devices should be both cheap and non-toxic; it should also exhibit a first-order magnetic transitions close to room temperature. The magnetic properties of Fe2P-related materials can be relevant in this context, since their magnetic properties can be finely tuned through the substitution of Fe by Mn and P by Si, As, Ge or B to meet the general requirements for a magnetocaloric device. An in-depth study has therefore here been made of the structural and magnetic properties of the (Fe,Mn)2(P,Si)-system. The phase diagram of the FeMnP1-xSix-system has been carefully re-examined. It is found to contain two single-phase regions: an orthorhombic Co2P-type structure (x < 0.15) and a hexagonal Fe2P-type structure (0.24 ≤ x < 0.50). Selected compounds within the Fe2P-type region of the phase diagram have been shown to exhibit potential for use in magnetic refrigeration applications. Neutron powder diffraction has here been used to determine the magnetic structures of selected crystalline compositions within the FeMnP1-xSix-system to gain a better understanding of its magnetic properties. The Fe2P-type region is mainly ferromagnetic, but an incommensurate antiferromagnetic structure has also been identified close to the Co2P/Fe2P-type phase border for x ≈ 0.25. The so-called ''virgin effect'' in the Fe2P-type region of the FeMn(P,Si) phase diagram is found to be accompanied by an irreversible structural phase transition induced by magnetostriction. This new phase is found to be preserved during successive cooling-heating cycles. Furthermore, the magnetic properties of the substituted Fe2P-type structure changes significantly for metal:non-metal ratios away from 2:1. Such deviations could well explain the apparently conflicting structure-property relationships described in earlier literature for the FeMnP1-xSix-system.
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Eckhardt, Kai, Volodymyr Bon, Jürgen Getzschmann, Julia Grothe, Florian M. Wisser et Stefan Kaskel. « Crystallographic insights into (CH3NH3)3(Bi2I9) : a new lead-free hybrid organic–inorganic material as a potential absorber for photovoltaics ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-219347.
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The crystal structure of a new bismuth-based light-absorbing material for the application in solar cells was determined by single crystal X-ray diffraction for the first time. (CH3NH3)3(Bi2I9) (MBI) is a promising alternative to recently rapidly progressing hybrid organic–inorganic perovskites due to the higher tolerance against water and low toxicity. Single crystal X-ray diffraction provides detailed structural information as an essential prerequisite to gain a fundamental understanding of structure property relationships, while powder diffraction studies demonstrate a high degree of crystallinity in thin films.
15
Carvajal, Martí Joan Josep. « Growth and characterisation of RbTiOPO4. A new self-frequency doubling crystal ». Doctoral thesis, Universitat Rovira i Virgili, 2003. http://hdl.handle.net/10803/9066.
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Growth and Characterisation of RbTiOPO4: (Nb,Ln). A New frequency Doubling Crystal.Joan Josep Carvajal Martí
Física I Cristal·lografia de Materials
Departament de Química Física i Inorgànica
Universitat Rovira i Virgili
Resum
Des que Schawlow i Townes varen publicar que el principi del M.A.S.E.R. es podia estendre a la part òptica de l'espectre electromagnètic, i un any i mig més tard Mainman demostrava el primer làser, la importància d'aquest, tant per la societat, s'ha anat incrementant. Avui, els làser formen part de la nostra vida quotidiana.
Actualment, l'interès en desenvolupar nous làser per l'emmagatzematge de dades i altres aplicacions s'ha incrementat gràcies a la recerca en làsers de semiconductors de banda ampla, generació d'harmònics per phase-matching en cristalls d'òptica no-lineal, quasi-phase-matching en cristalls, fibres òptiques i altres guies d'ona, i làsers d'up-conversion en cristalls i fibres. Els làsers d'estat sòlid compactes són útils en una amplia gamma d'aplicacions, com l'emmagatzematge de dades en alta densitat, projecció d'imatges en color, impressió làser, medicina, substitució dels làsers d'Ar, biofluorescència, comunicacions submarines, litografia estereogràfica, teràpia fotodinàmica....
Aquests nous làsers es poden aconseguir per processos d'up-conversion, que emeten a una longitud d'ona més curta que la de bombeig. Una alternativa interessant és la conversió de freqüència per processos d'òptica no-lineal. Els cristalls autodobladors de freqüència són cristalls d'òptica no-lineal amb posicions estructurals ocupades per ions actius làser, preferiblement Yb3+, que poden combinar l'emissió làser al voltant d'1 um amb la generació de segon harmònic de la matriu per produir emissió verda per autodoblatge de freqüència.
L'objectiu principal d'aquesta Tesi Doctoral ha estat l'obtenció de cristalls de la família del KTiOPO4, coneguts per les seves excel·lents propietats d'òptica no-lineal, dopats amb ions lantànids (Ln).
Hem mostrat que és poden obtenir cristalls de RbTiOPO4: (Nb,Ln) de bona qualitat òptica per la tècnica top-seeded solution growth amb un refredament lent de la solució, de mida útil per posteriors caracteritzacions i aplicacions, i amb una concentració de Ln similar a l'obtinguda en altres matrius làser i un codopant, que afavoreix l'entrada d'ions lantànids en la matriu a l'hora que fa de compensador de càrrega, com és el niobi (Nb5+).
El refinament de l'estructura ha demostrat que tant el Nb com els lantànids substitueixen únicament al Ti en la xarxa cristal·lina. Mentre que el Nb5+ només substitueix al Ti en la posició Ti (1), degut a un efecte electrostàtic més que no pas estèric, els ions lantànids substitueixen als àtoms de Ti en els octàedres Ti(1)O6 i Ti(2)O6 amb la mateixa probabilitat. Un altre aspecte a destacar és l'habilitat del material per tal d'autocompensar-se elèctricament de la substitució pentavalent del Nb5+ a través de la creació de vacants de rubidi. L'evolució d'aquesta estructura amb la temperatura mostra com el canvi de fase de l'estructura ferroelèctrica depèn del contingut en Nb i que la substitució de Ti4+ pel parell (Nb5+-Rb+) estabilitza la fase d'alta temperatura d'aquests materials.
La caracterització òptica de la matriu cristal·lina ha mostrat que l'increment de la birefringència de cristall possibilita l'increment de l'interval de doblatge de longituds d'ona que es pot efectuar amb aquests cristalls. L'àmplia finestra òptica juntament amb l'eficiència de conversió a segon harmònic mostren que aquesta és una bona matriu per hostatjar ions lantànids. Aquestes excel·lents propietats es mantenen fins i tot quan els ions lantànids es troben al cristall. Finalment, la caracterització espectrocòpia del ions actius ha mostrat que es pot obtenir una emissió eficient per part dels dos ions. Er3+b3+ la banda d'emissió ampla i l'elevada vida mitja obtingudes obren la possibilitat d'utilitzar aquests cristalls en aplicacions sintonitzables i de subpicosegons.
Totes aquestes observacions ens duen a concloure que amb aquests cristalls es pot obtenir un nou material autodoblador de freqüència.
Paraules clau: Òptica No-Lineal, Generació de Segon Harmònic, Autodoblatge de freqüència, Top-Seeded Solution Growth, KTiOPO4, RbTiOPO4, Difacció de raig X, Difracció de neutrons de pols.
Growth and characterisation of RbTiOPO4: (Nb, Ln). A New Self-frequency
Doubling Crystal.
Joan Josep Carvajal Martí
Física I Cristal·lografia de Materials
Departament de Química Física i Inorgànica
Universitat Rovira i Virgili
Abstract
Since Schawlow and tornes reported that it should be possible to extend the maser principle to the optical frequency part of the spectrum and only one and a half years later. Mainman demonstrated the first laser, the importance of lasers to both science and society has increased dramatically. Today lasers are part of everyday life.
Actually, the interest in developing compact blue and green laser sources for data storage and display applications has increased due to promising investigations into wide-gap semiconductor diode lasers, harmonic generation by phase matching in non-linear crystals, quasi-phase-matching in bulk, optical fibres and other waveguides, and up conversion lasers in crystals and fibers. Compact all-solid-state laser sources are needed for a variety of applications such as colour projection, high-density optical data storage, laser printing, medicine, Argon-laser replacement, biofluorescence, underwater communications, stereo lithography, photodynamic therapy.
A class of these sources is achieved with up-conversion lasers emitting at a shorter wavelength than the pump source. An alternative to up-conversion lasing is frequency conversion by non-linear optical processes such as frequency doubling and sum-frequency mixing. Self-frequency doubling crystals are non-linear optical crystals with suitable sites for laser-active ions, preferably Yb3+, which can combine the 1 um laser emission of the active ions with the second harmonic generation properties of the host to produce green-laser radiation by self-frequency doubling.
The aim of this Thesis was to investigate how to obtain crystals of the KTiOPO4 family, which are known for their excellent non-linear optical properties, doped with lanthanide (Ln) ions.
This Thesis shows that high-optical quality RbTiOPO4(Nb,Ln) single crystals can be obtained by the top-seeded solution growth technique together with a slow-cooling of the solution, with large volumes useable for later characterisations and technical applications, and with a similar Ln concentration to that of other laser matrices. We introduced a codopant that enhances the concentration of Ln in the crystals at the same time that compensate the electrical charge of the framework.
The refinement of the structure demonstrates that Nb and Ln ions only go to the Ti positions. Then, while Nb only substitutes Ti in the Ti(1) crystallographic position due to an electrostatic effect that an steric one, the lanthanide ion substitute Ti in both Ti(1)O6 octahedra with the same probability. Another interesting aspect to notice is the ability of the material to self-compensate the excess of electrical charge introduced by the pentavalent substitution of Nb5+ by the creation of Rubidium vacancies. The evolution of this structure with temperature showed that the transition from the ferroelectric phase to the paraelectric phase depended on the Nb content in the crystals, and that substituting Ti4+ by the (Nb5+-Rb+) pair stabilises the cubic high-temperature phase of these crystals. The optical characterisation of the host showed that the increase of birefringence in the crystals containing Nb causes the limit fundamental wavelength, at which second harmonic generation can be obtained, to shift to lower wavelengths. The large transparency window of the material and the conversion efficiency to second harmonic generation showed that this crystal is a good matrix to host lanthanide ions. These excellent properties are maintained even when the lanthanide ions is hosted in the crystalline matrix. Finally, the spectroscopic characterisation of the active ions showed that efficient emission can be obtained for Er3+ at 1.5 and 1.0 um, respectively. In the case of Yb3+ the broad emission band and the large lifetime obtained open up the possibility to use these crystals in tunable and subpicosecond applications.
All these observations seems to converge in the conclusion that with these crystals a new self-frequency doubling material can be obtained.
Keywords: Non-linear Optics, Second Harmonic Generation, Self-frequency Doubling, Top-Seeded Solution Growth, KTiOPO4, RbTiOPO4, X-ray Diffraction, Powder Neutron Diffraction.
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Kifune, Koichi, Miho Fujita, Mitsuru Sano, Motoharu Saitoh et Koh Takahashi. « Electrochemical and Structural Properties of a 4.7 V-Class LiNi0.5Mn1.5 O 4 Positive Electrode Material Prepared with a Self-Reaction Method ». The Electrochemical Society, 2004. http://hdl.handle.net/2237/18424.
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Redha, Batul H. « Impact of mixed solvent on co-crystal solubility, ternary diagrams and crystallisation scale-up. Crystallisations of Isonicotinamide ¿Benzoic Acid Co-crystals from Ethanol ¿Water Co-solvent System ». Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5683.
Texte intégralRésumé :
The production of stable solid crystalline material is an important issue in the pharmaceutical industry and the challenge to control the desired active pharmaceutical ingredient (API) with the specific chemical and physical properties has led to more development in the drug industry. Increasing the solubility and the dissolution of the drug will increase its bioavailability; therefore the solubility can be improved with the change in the preparation method. The formation of co-crystals has emerged as a new alternate to the salts, hydrates and solvate methods since the molecules that cannot be formed by the usual methods might crystallise in the form of co-crystals.
Co-crystals are multicomponent crystals which can be known as supramolecules and are constructed by the non covalent bonds between the desired former and co-former.
Therefore the synthon approach was utilised to design co-crystals with the specific properties, this involves the understanding of the intermolecular interactions between these synthons. These interaction forces can be directed to control the crystal packing in the design of the new crystalline solid with the desired chemical and physical properties. The most familiar synthon was the amide group with its complementary carboxylic group, in this work isonicotinamide and benzoic acid were chosen to design co-crystal and much literature exist that introduce the determination of co-crystal growth from these two compounds.
The growth of co-crystals was carried out in water, ethanol and ethanol / water mixed solvent (30 - 90 % ethanol) by utilising the Cryo-Compact circulator. Co-crystals (1:1) and (2:1) were grown in ethanol and water respectively and a mixture of both phases were grown in the mixed solvent. All the phases were examined by powder X-ray diffraction (PXRD), Raman, Infrared and 1H-NMR spectroscopy. The solubility of isonicotinamide, benzoic acid, co-crystals (1:1) and (2:1) in water, ethanol and ethanol/water mixed solvent (30 - 90 % ethanol) were determined at 25 °C, 35 °C and 40 °C by utilising the React-Array Microvate.
It was important to understand some of the thermodynamic factors which control the formation of these polymorphs such as the change in the enthalpy and the change in the entropy. Also it was important to study the pH behaviour during dissolution of the former, co-former and co-crystals in water, ethanol and ethanol/water mixed solvent (30 - 90 % ethanol) in-order to examine the affect of the solvent composition on the solubility and to identify if some ions were formed during the dissociation and how this could affects the formation of co-crystals.
A discussion has been introduced in this research of how similar solubility of the compounds maps the formation of the typical ternary phase diagram of the mixture of 1:1 while compounds with different solubility maps the formation of skewed phase diagram as shown in section 1.6.2.3. In this project an isotherm ternary phase diagram at 20 °C and 40 °C was constructed to map the behaviour of benzoic acid and isonicotinamide and to show all possible phases formed and the regions where all phases are represented in the ternary phase diagram were determined by the slurry method.
The ternary phase diagram was used to design a drawn out and cooling crystallisation at 100 cm3 solution of 50 % ethanol / water mixed solvent and a study of the impact of seeds of co-crystals 1:1 on the cooling crystallisation method.
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Eckhardt, Kai, Volodymyr Bon, Jürgen Getzschmann, Julia Grothe, Florian M. Wisser et Stefan Kaskel. « Crystallographic insights into (CH3NH3)3(Bi2I9) : a new lead-free hybrid organic–inorganic material as a potential absorber for photovoltaics ». Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A30174.
Texte intégralRésumé :
The crystal structure of a new bismuth-based light-absorbing material for the application in solar cells was determined by single crystal X-ray diffraction for the first time. (CH3NH3)3(Bi2I9) (MBI) is a promising alternative to recently rapidly progressing hybrid organic–inorganic perovskites due to the higher tolerance against water and low toxicity. Single crystal X-ray diffraction provides detailed structural information as an essential prerequisite to gain a fundamental understanding of structure property relationships, while powder diffraction studies demonstrate a high degree of crystallinity in thin films.
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Weston, Laura. « Computational characterisation of organic molecules for electronic applications and an experimental study of cocrystals for electronic devices ». Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/computational-characterisation-of-organic-molecules-for-electronic-applications-and-an-experimental-study-of-cocrystals-for-electronic-devices(0d1a24ea-3241-40cf-bafa-6be179ba4c26).html.
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A range of small molecules of interest for use in organic semiconductor devices were studied computationally. Trends in geometry, absorption spectra, molecular orbitals, electrostatic potentials, reorganisation energies were studied. Results suggest that, as with acenes, the performance of non-linear cata-condensed polyaromatic hydrocarbons improves as number of fused benzene rings increases. The torsion in these molecules did not appear to have a large impact on the conjugation across the core and little effect on the absorption spectra, although it did affect the reorganisation energies on which charge mobilities depend. Computational studies of mobilities of anthradithiophene molecules were broadly able to reproduce trends seen experimentally and emphasised the importance of crystal morphology. Experimental work was also carried out to search for cocrystals between anthradithiophene derivatives. Many examples were found with some mixtures forming different cocrystals at different mixture ratios. These results were rationalised by a computational study that showed molecules which had a similar binding energy were more likely to be able to form cocrystals. Cocrystal devices were fabricated and 3 out of 7 showed a larger mobility than devices made out of its constituent materials alone. The best of these had a mobility 65% higher than a device made out of the constituent material with the largest mobility. An energy decomposition analysis was carried out on a novel thallophilic system, a complex of thallium with a neutral β-triketimine ligand which was found to form dimers with close Tl-Tl interactions. Calculations show the electrostatic interaction to be repulsive for the dimer with no counter ions, but attractive when 3,5-bistrifluoromethylphenyl borate counter ions are included. This suggests the metallophilic interaction is counter ion-mediated, requiring the anions to provide favourable electrostatics, even in the case of spatially diffuse and distant counter ions such used here. To enable the studies described here software was written for simulating absorption spectra. An implementation into the Gaussian Suite of programs of an energy decomposition scheme and its extension to include an empirical dispersion correction was also carried out.
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Hinrichsen, Bernd. « Two-dimensional X-ray powder diffraction ». [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-33946.
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Eriksson, Therese. « The Structural Basis for Magnetic Order in New Manganese Compounds ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5746.
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Escudero, Adán Eduardo Carmelo. « High resolution X-ray single crystal diffraction ». Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/586278.
Texte intégralRésumé :
Aquesta tesi doctoral descriu l'ús de dades d'alta resolució de difracció de raigs X de monocristall per a la
obtenció de mapes experimentals detallats de distribució de densitat de càrrega. Aquests mapes serveixen per
evidenciar experimentalment l'existència d'interaccions intra- i inter-moleculars febles dins de l'estructura
del vidre. Els mapes de densitat de càrrega s'obtenen mitjançant un refinament multipolar de l'estructura
cristal·lina. En concret, aquest treball se centra en evidenciar experimentalment les interaccions atractives no
covalent recentment descrites teòricament i que donen lloc a la formació d'enllaços de tipus "sigma i pi hole".
Els termes enllaços de Triel, tetrel, pnictogen i chalcogen van ser recentment introduïts per referir-se a aquestes
interaccions en funció del grup (14, 15 i 16) al qual pertany l'àtom implicat com a centre electrofílic. el
fet que aquestes interaccions siguin molt febles fa necessari l'obtenció de mapes de densitat electrònica
molt precisos. També s'han utilitzat aquests mapes de densitat electrònica per determinar experimental el
moment quadrupolar i el potencial electrostàtic molecular d'una sèrie d'anells de fenil amb diferents
substituents. Les dades experimentals obtingudes d'aquesta manera han servit per validar els resultats de càlculs
teòrics.Esta tesis doctoral describe el uso de datos de alta resolución de difracción de rayos X de monocristal para la obtención de mapas experimentales detallados de distribución de densidad de carga. Estos mapas sirven para evidenciar experimentalmente la existencia de interacciones intra- e inter-moleculares débiles dentro de la estructura del cristal. Los mapas de densidad de carga se obtienen mediante un refinamiento multipolar de la estructura cristalina. En concreto, este trabajo se centra en evidenciar experimentalmente las interacciones atractivas no covalente recientemente descritas teóricamente y que dan lugar a la formación de enlaces de tipo "sigma y pi hole". Los términos enlaces de Triel, tetrel, pnictogen y chalcogen fueron recientemente introducidos para referirse a estas interacciones en función del grupo (14, 15 y 16) al que pertenece el átomo implicado como centro electrofílico. El hecho de que estas interacciones sean muy débiles hace necesario la obtención de mapas de densidad electrónica muy precisos. También se han utilizado estos mapas de densidad electrónica para determinar experimental el momento cuadrupolar y el potencial electrostático molecular de una serie de anillos de fenilo con diferentes sustituyentes. Los datos experimentales obtenidos de esta forma han servido para validar los resultados de cálculos teóricos.
radiación de molibdeno para asignar la configuración absoluta de una serie de moléculas orgánicas. Las moléculas medidas fueron seleccionadas teniendo en cuenta que el elemento más pesado de su composición química fuera el oxígeno. Es bien conocido que la dispersión anómala de este tipo de compuestos es muy débil y dificulta la asignación de configuración absoluta mediante esta técnica. El resultados de este trabajo demuestran que la metodología empleada es muy efectivo para poder asignar inequívocamente la configuración absoluta correcta en este tipo de moléculas. This thesis uses high resolution single crystal X-ray diffraction data in order to obtain experimental detailed charge density distribution maps that can exhibit intra and intermolecular interactions. The charge density maps are obtained through the multipolar refinement. Particularly, this work focuses in lasts classified non-covalent attractive interactions due to sigma and pi holes, triel, tetrel, pnictogen and chalcogen bonds. The weakness of these interactions make necessary very accurate and precise maps. In the same manner, in this works they have been determined the quadrupolar moment and the molecular electrostatic potential of a series of phenyl rings substituted with different chemical groups. The experimental data obtained in this way have been used to validate theoretical predictions. Eventually in this work, high resolution single crystal X-ray diffraction data using molybdenum radiation has been employed to assign the absolute configuration of a series of organic molecules. The measured molecules were selected containing oxygen as heaviest atom since the anomalous dispersion of these kind of compounds is very weak. The use of high resolution data has been proved to be effective in order to unequivocally assign the correct absolute configuration in this kind of molecules.
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Suffren, Yan. « Synthèses et études structurales de complexes à oxo-anion de l'iode (V) : vers de nouveaux matériaux pour l'optique non linéaire quadratique ». Grenoble, 2010. http://www.theses.fr/2010GRENV081.
Texte intégralRésumé :
Le sujet de thèse a porté sur l'élaboration de iodates métalliques, matériaux pour l'ONL quadratique, qui permettraient de développer des dispositifs optiques à large bande de transparence du visible à l'IR lointain, couvrant les fenêtres de transparence II et III de l'atmosphère. La découverte de NaI3O8 présentant les principales caractéristiques des iodates a ouvert la voie à la recherche et caractérisation de nouvelles phases contenant le nouvel oxoanion [I3O8]- de l'iode (V). Des calculs DFT ont été effectués pour décrire les liaisons I-O dans le composé Rb2(IO3)(I3O8)(HIO3)2(H2O). En parallèle, la cristallogenèse de cristaux millimétriques de NaI3O8 a été réalisée par ALT puis par circulation pour déterminer ses propriétés ONL sur monocristaux. D'autres phases contenant l'anion [IO3]- ont été obtenues par synthèse en solution d'acide nitrique concentré, par voie hydrothermale, ou par voie solide sous haute pression. Les premières caractérisations de TiO(IO3)2 montrent que c'est un matériau potentiellement intéressant pour l'ONL. L'alternance de liaisons courtes et longues, similaire à celles observées dans KTP, laisse présager des transferts de charge importants le long des chaines ***O-Ti-O***. Les solutions solides beta-La1-xLnx(IO3)3 présentent une transition structurale displacive réversible en yama -La1-xLnx(IO3)3. La température de transition de la phase non centrosymétrique aux propriétés non linéaires évolue en fonction de la taille et du pourcentage d'ions dopants insérés. Des études de photoluminescence de certaines matrices dopées avec des ions Nd3+ et Yb3+ont été réaliséesThe thesis focused on the synthesis of metallic iodates, materials for quadratic NLO, in order to develop optical devices with a broad band of transparency from visible to far infrared, covering the II and III transparency windows of the atmosphere. The discovery of NaI3O8, possessing the main feature of iodates, has opened the way for research and characterization of new phases containing the new oxo-anion [I3O8]- of iodine(V). DFT calculations were performed to describe the I-O bonds in the Rb2(IO3)(I3O8)(HIO3)2(H2O) compound. Furthermore, the crystal growth of millimeter size NaI3O8 crystals was performed by slow lowering of temperature and by solution circulation method to determine NLO properties on single crystals. Other phases containing the [IO3]- anion were obtained by synthesis in concentrated nitric acid solution, by hydrothermal or by solid state route under high pressure. The first characterizations of TiO(IO3)2 show a potentially interesting material for the NLO. The alternation of long and short bond lengths, similar to that observed in KTP, suggests significant charge transfer along the chains ***O-Ti-O***. Solid solutions beta -La1-XLnX(IO3)3 present a reversible structural transition in yama -La1-XLnX(IO3)3. The transition temperature for acentric phase with nonlinear properties varies according to the size and percentage of doping ions. Photoluminescence studies of some matrixes doped with Nd3+ and Yb3+ were performed
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Sheridan, Andrew Keith. « Kinetics and temperature- and pressure-induced polymorphic phase transformations in molecular crystals ». Thesis, King's College London (University of London), 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322597.
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Barnett, Stephanie Jayne. « X-ray powder diffraction studies of ettringite and related systems ». Thesis, Staffordshire University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244708.
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Tremayne, Maryjane. « Ab initio structure determination from X-ray powder diffraction data ». Thesis, University of St Andrews, 1995. http://hdl.handle.net/10023/6503.
Texte intégralRésumé :
Many important crystalline solids cannot be prepared in the form of single crystals of sufficient size and quality for single crystal X-ray diffraction studies, and in such cases it is essential that structural information can be extracted from powder diffraction data. In this thesis, a number of crystal structures have been determined directly from X-ray powder diffraction data recorded on a conventional laboratory instrument, and the limitations of this technique explored using both conventional and new more sophisticated methods of structure solution. This work has focussed mainly on the more complex problem of molecular systems. The Patterson method has been applied to the determination of a simple unknown inorganic structure, lithium perchlorate, whereas conventional direct methods have been used in the determination of a number of organic structures, including the previously unknown crystal structure of 1,3,4,6-tetrathiopentalene-2,5-dione and formylurea - the first previously unknown organic structure containing only light atoms to be solved by this technique. The combined maximum entropy and likelihood method has been applied to determinate two crystal structures, lithium triflate and p-toluenesulphonhydrazide. Further developments of this technique are also discussed and illustrated in the structure solution of a previously known system. A Monte Carlo algorithm for ab initio crystal structure determination from powder diffraction data has also been developed, and the success of this method demonstrated by its application to the determination of several known structures, and the previously unknown crystal structure of p-bromophenylacetic acid. The effect of data range on the quality of structure solution obtained from both direct methods and the maximum entropy and likelihood method is also discussed.
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Krause, Lennard. « Assessment of Single Crystal X-ray Diffraction Data Quality ». Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://hdl.handle.net/11858/00-1735-0000-0023-3DD4-A.
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Bayuadri, Cosmas. « Stability of sodium sulfate dicarbonate (~2Na₂CO₃• Na₂SO₄) crystals ». Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11507.
Texte intégralRésumé :
Research on salts species formed by evaporation of aqueous solution of Na2 in the early 1930s. The thermodynamic, crystallographic and many other physical and chemical properties of most of the species formed from this solution has been known for decades. However, there was no complete information or reliable data to confirm the existence of a unique double salt that is rich in sodium carbonate, up until five years ago when a research identified the double salt (~2Na ₂ CO ₃ • Na ₂ SO ₄) from the ternary system Na₂CO ₃Na₂SO ₄ H₂O. Crystallization of this double salt so called sodium sulfate dicarbonate (~2Na ₂ CO ₃ • Na ₂ SO ₄) is known to be a primary contributor to fouling heat transfer equipment in spent-liquor concentrators used in the pulp and paper industry. Therefore, understanding the conditions leading to formation of this double salt is crucial to the elimination or reduction of an industrial scaling problem. In this work, double salts were generated in a batch crystallizer at close to industrial process conditions. X-ray diffraction, calorimetry, and microscopic observation were used to investigate the stability of the salts to in-process aging, isolation and storage, and exposure to high temperature. The results show that care must be taken during sampling on evaporative crystallization. Two apparent crystal habits were detected in the formation of sodium sulfate dicarbonate; the favored habit may be determined by calcium ion impurities in the system. The results also verify that sodium sulfate dicarbonate exists as a unique phase in this system and that remains stable at process conditions of 115-200℃
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Bell, A. M. T. « Structural studies using synchrotron X-ray powder diffraction and other techniques ». Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596545.
Texte intégralRésumé :
Chapter 1 gives an introduction to X-ray and neutron powder diffraction and the use of these techniques for crystal structure determination and refinement. The Rietveld structure refinement method is described and examples of different methods of structure determination from powder diffraction data are given. The techniques of EXAFS and Mössbauer spectroscopy, which were used to provide additional structural information, are also introduced. Chapter 2 describes the different radiation sources and experimental techniques used in this work. Chapter 3 describes a structural study of magnetite, Fe3O4, below the Verwey phase transition (120 K). The P2/c structure of Fe3O4 at 60 K has been refined with lattice parameters of a = 5.9412(3) Å, b = 5.9290(3) Å, c = 16.789(1) Å and β = 90.196(4). A variable temperature study of the Fe3O4 lattice parameters between 2-280 K shows this transition is first-order. An EXAFS study between 8-270 K shows that there is no significant change in the average Fe-O distance in Fe3O4 around the transition. Chapter 4 describes a structural study on a material related to magnetite, Fe2OBO3. Two phase transitions have been found for this material. The first of these is due to magnetic ordering and takes place at 155 K. The second is due to charge ordering and takes place at 315 K, this is a structural (P21/c ↔ Pnma) transition. Chapter 5 describes a resonant scattering experiment done on CsI. Resonant scattering parameters have been refined from synchrotron X-ray powder diffraction data collected at room temperature and at 4 K close to the Cs and I K-edges. The refined f parameters are -6.2(2) e/atom (Cs, λ = 0.3453 Å), -9.0(I) e/atom (I, λ = 0.374105 Å) and -6.2(2) e/atom (I, 4 K, λ = 0.37367 Å). Chapter 6 describes the ab initio structure determination of 4-(2'3'4'-trifluorophenyl)-1235 dithiadiazolyl (C7S2N2F3H2; P2/n, a = 11.543(4) Å, b = 20.666(8) Å, c = 7.045(2) Å and β = 100.35(4) using synchrotron X-ray powder diffraction data. A global optimisation method was used to provide a starting model for Rietveld refinement.
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Seaton, Colin Cormack. « Novel methods of structure determination from X-ray powder diffraction data ». Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396462.
Texte intégralRésumé :
The determination of crystal structures from powder diffraction data is a field that is rapidly expanding due to a range of computational and experimental developments. A major driving force of this expansion is the continuing development of direct space methods of structure solution. This work will show the development of the program POSSUM as a suite of direct space structure determination methods and its subsequent successful application to a number of molecular organic and inorganic materials whose crystal structures were previously unknown. Direct space methods utilise global optimisation algorithms to locate the crystal structure. This work describes the successful application of the differential evolution optimisation algorithm to structure determination from powder diffraction. Differential evolution is shown to be a robust and efficient optimisation technique with the limited number of control parameters associated with the method ensuring that optimisation of the searching is easily achieved. Investigation into improving the computer performance of the method also focused on reduction of the time taken to evaluate agreement between experimental and calculated patterns through the application of the discrete wavelet transform. This effectively reduces the number of points in the powder pattern, yet retains the same level of information as the original data set and is shown to illustrate good discrimination between solutions generated in a direct space structure solution.
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Day, Sarah Joanne. « Studies of cosmic dust analogues using synchrotron X-ray powder diffraction ». Thesis, Keele University, 2014. http://eprints.keele.ac.uk/1215/.
Texte intégralRésumé :
The structural evolution of cosmic dust analogues has been investigated using in situ synchrotron X-ray powder diffraction (SXPD) at the Diamond Light Source. Amorphous Mg/Ca silicates are produced as analogues of cosmic dust using a modified sol-gel method. They are studied under non-ambient temperature and pressure conditions using in situ powder diffraction, complemented by FTIR and Raman spectroscopy. The solid-state mineralisation of amorphous grains is observed by thermal annealing and the results of this allow the environmental conditions leading to the formation of crystalline dust grains in astrophysical environments to be constrained. The solid-gas carbonation of amorphous Ca-rich silicates is studied using in situ SXPD and analysed using full-profile fitting techniques, while the effect of ex situ carbonation on the short range ordering of amorphous grains is investigated using high energy SXPD and Pair Distribution Function (PDF) analysis. The formation of a metastable calcium carbonate phase (vaterite) is observed and the importance of this in relation to astrophysical environments is discussed. In situ Raman and SXPD data of CO2 clathrate hydrates are presented and the importance of the Raman data obtained here with relevance to future remote sensing missions to Solar System bodies is discussed. This work indicates the importance of laboratory work to the field of astrophysics and provides novel experimental approaches to aid our understanding of astrophysical processes.
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Leonardi, Alberto. « Molecular Dynamics and X-ray Powder Diffraction Simulations : Investigation of nano-polycrystalline microstructure at the atomic scale coupling local structure configurations and X-ray powder Diffraction techniques ». Doctoral thesis, Università degli studi di Trento, 2012. https://hdl.handle.net/11572/368091.
Texte intégralRésumé :
Atomistic simulations based on Molecular Dynamics (MD) were used to model the lattice distortions in metallic nano-polycrystalline microstructures, with the purpose of supporting the analysis of the X-ray powder diffraction patterns with a better, atomic level understanding of the studied system.
Complex microstructures were generated with a new modified Voronoi tessellation method which provides a direct relation between generation parameters and statistical properties of the resulting model. MD was used to equilibrate the system: the corresponding strain field was described both in the core and in surface regions of the different crystalline domains. New methods were developed to calculate the strain tensor at the atomic scale.
Line Profile Analysis (LPA) was employed to retrieve the microstructure information (size and strain effects) from the powder diffraction patterns: a general algorithm with an atomic level resolution was developed to consider the size effects of crystalline domains of any arbitrary shape. The study provided a new point of view on the role of the grain boundary regions in nano-polycrystalline aggregates, exploring the interference effects between different domains and between grain boundary and crystalline regions. Usual concepts of solid mechanics were brought in the atomistic models to describe the strain effects on the powder diffraction pattern. To this purpose the new concept of Directional - Pair Distribution Function (D-PDF) was developed. D-PDFs calculated from equilibrated atomistic simulations provide a representation of the strain field which is directly comparable with the results of traditional LPA (e.g. Williamson-Hall plot and Warren-Averbach method).
The D-PDF opens a new chapter in powder diffraction as new insights and a more sound interpretation of the results are made possible with this new approach to diffraction LPA.
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Leonardi, Alberto. « Molecular Dynamics and X-ray Powder Diffraction Simulations : Investigation of nano-polycrystalline microstructure at the atomic scale coupling local structure configurations and X-ray powder Diffraction techniques ». Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/843/1/PhDThesis_ALeonardi.pdf.
Texte intégralRésumé :
Atomistic simulations based on Molecular Dynamics (MD) were used to model the lattice distortions in metallic nano-polycrystalline microstructures, with the purpose of supporting the analysis of the X-ray powder diffraction patterns with a better, atomic level understanding of the studied system.
Complex microstructures were generated with a new modified Voronoi tessellation method which provides a direct relation between generation parameters and statistical properties of the resulting model. MD was used to equilibrate the system: the corresponding strain field was described both in the core and in surface regions of the different crystalline domains. New methods were developed to calculate the strain tensor at the atomic scale.
Line Profile Analysis (LPA) was employed to retrieve the microstructure information (size and strain effects) from the powder diffraction patterns: a general algorithm with an atomic level resolution was developed to consider the size effects of crystalline domains of any arbitrary shape. The study provided a new point of view on the role of the grain boundary regions in nano-polycrystalline aggregates, exploring the interference effects between different domains and between grain boundary and crystalline regions. Usual concepts of solid mechanics were brought in the atomistic models to describe the strain effects on the powder diffraction pattern. To this purpose the new concept of Directional - Pair Distribution Function (D-PDF) was developed. D-PDFs calculated from equilibrated atomistic simulations provide a representation of the strain field which is directly comparable with the results of traditional LPA (e.g. Williamson-Hall plot and Warren-Averbach method).
The D-PDF opens a new chapter in powder diffraction as new insights and a more sound interpretation of the results are made possible with this new approach to diffraction LPA.
34
Gonthier, Sabine. « Systèmes modèles du réseau carré frustré : synthèses, caractérisations structurales et propriétés magnétiques : étude en fonction de la température ». Toulouse 3, 2005. http://www.theses.fr/2005TOU30096.
Texte intégralRésumé :
Ce travail est consacré à la synthèse et aux études structurales et magnétiques de systèmes frustrés sur un réseau carré : VMoO5 et Li2V1-xTixSiO5. Après s'être intéressé à l'élaboration de VMoO5, ses propriétés magnétiques ont été corrélées à des études à basse température par diffraction neutronique et par rayonnement synchrotron sur poudre, celles-ci étant motivées par la mise en évidence d'une instabilité structurale concomitante de l'instauration des corrélations magnétiques à courte portée. Il a été montré que VMoO5 correspondait à un réseau 2D antiferromagnétique frustré. Les études par diffraction des neutrons ont permis de mettre en évidence l'existence d'un ordre magnétique de Néel en dessous de 40K. L'étude des phases Li2V1-xTixSiO5 a montré que la dilution magnétique de Li2VSiO5 permet de moduler les valeurs de ses interactions d'échange, ce qui rend ce système très prometteur pour l'étude du diagramme de phase magnétique des systèmes frustrés sur un réseau carréWe present synthesis, structural and magnetic characterizations of two frustrated systems on a square lattice : VMoO5 and Li2V1-xTixSiO5. The first part is related to the VMoO5 phase. After introducing its elaboration, its magnetic properties are correlated with neutron and synchrotron powder diffraction results at low temperature. These investigations are motivated by the presence of a structural instability, which occurs concomitantly with apparition of magnetic short-range correlations. VMoO5 is shown to be a frustrated 2D antiferromagnet. Moreover, neutron diffraction experiments allow the determination of the magnetic order below 40K. The study of the Li2V1-xTixSiO5 phases shows that magnetic dilution of Li2VSiO5 allows to modulate exchange interactions values. It is particularly interesting because it emphasizes the possibility to investigate the whole magnetic phase diagram of frustrated systems on a square lattice by means of well-chosen substitutions
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Wilkinson, Angus P. « Some applications of synchrotron X-ray powder diffraction to solid-state chemistry ». Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302908.
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Wang, Te-Kang. « A powder X-ray diffraction study of two aluminum-lithium based alloys ». Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/43736.
Texte intégralRésumé :
Approved for public release; distribution is unlimited.The microstructures of solution treated, quenched and aged A1-2.5 wt. %Li and A1-2.0 wt.%Li-2.76 wt.%Mg-1.03 wt.%Cu alloys were studied by powder X- ray diffraction. The as-quenched alloys showed extensive X-ray line broadening due to particle size effects and the intensity measurements indicated a significant amount ordering in the as-quenched state. These results were interpreted using a 'spinodal ordering' model which suggests that A1-Li-based alloys order during quenching and then spinodally decompose into regions of order and disorder so that the final microstructure comprises small ordered regions (size 40 nm) in a disordered matrix Studies on the aged A1-2.5 wt.%Li alloy indicated that after initial short-time aging, particle growth follows Ostwald ripening kinetics in agreement with previous work. Studies on the aged quaternary alloy indicated that T1 and S phases grow in this system so that precipitates are not a dominant strengthening mechanism in this alloy.
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Sitepu, Husinsyah. « Characterisation of preferred orientation in crystalline materials by x-ray powder diffraction ». Thesis, Curtin University, 1991. http://hdl.handle.net/20.500.11937/1897.
Texte intégralRésumé :
Texture, i.e. preferred orientation, can cause large systematic errors in quantitative analysis of crystalline materials using x-ray powder diffraction (XRPD) data. Various mathematical forms have been proposed for the application of preferred orientation corrections. The most promising of these appears to be the single-parameter March (1932) model proposed by Dollase (1986).Li and O'Connor (1989) applied the March model to determine the level of preferred orientation in various gibbsites using two procedures. The first involved the Rietveld (1969) least squares pattern-fitting method. Each pattern was Rietveld-analysed in two ways, initially assuming random orientation of the crystallites and subsequently with the March model. The second procedure for preferred orientation analysis, described here as the line ratio method, determines preferred orientation factors according to the intensity ratios of carefully selected line pairs.In the thesis the procedures proposed by Li and O'Connor for texture analysis have been evaluated with XRPD data sets for molybdite, calcite and kaolinite. The results indicate that while the March formula improves agreement between the' calculated and measured patterns in Rietveld analysis, other forms of systematic error in the intensity data appear to limit the effectiveness of the March formula in general. It has been found also that the line ratio method improves agreement between the data sets, but less effectively than the Rietveld method. It is proposed that extinction is likely to be the most influential source of systematic error competing with texture.
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Sitepu, Husinsyah. « Characterisation of preferred orientation in crystalline materials by x-ray powder diffraction ». Curtin University of Technology, School of Physical Sciences, 1991. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10554.
Texte intégralRésumé :
Texture, i.e. preferred orientation, can cause large systematic errors in quantitative analysis of crystalline materials using x-ray powder diffraction (XRPD) data. Various mathematical forms have been proposed for the application of preferred orientation corrections. The most promising of these appears to be the single-parameter March (1932) model proposed by Dollase (1986).Li and O'Connor (1989) applied the March model to determine the level of preferred orientation in various gibbsites using two procedures. The first involved the Rietveld (1969) least squares pattern-fitting method. Each pattern was Rietveld-analysed in two ways, initially assuming random orientation of the crystallites and subsequently with the March model. The second procedure for preferred orientation analysis, described here as the line ratio method, determines preferred orientation factors according to the intensity ratios of carefully selected line pairs.In the thesis the procedures proposed by Li and O'Connor for texture analysis have been evaluated with XRPD data sets for molybdite, calcite and kaolinite. The results indicate that while the March formula improves agreement between the' calculated and measured patterns in Rietveld analysis, other forms of systematic error in the intensity data appear to limit the effectiveness of the March formula in general. It has been found also that the line ratio method improves agreement between the data sets, but less effectively than the Rietveld method. It is proposed that extinction is likely to be the most influential source of systematic error competing with texture.
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Lubhelwana, Siyanda. « Crystal isostructurality and X-ray diffraction studies of cyclodextrin inclusion compounds ». Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/6324.
Texte intégralRésumé :
Includes bibliographical references.The first part of this dissertation is an update on the isostructurality method of PXRD analysis (lsoPXRD), the last update having been published in 2001 The scope of the isostructurality part of this dissertation includes organic inclusion complexes of all three natural cyclodextrins (a-,
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Phillips, Pepe Louise. « Characterization of liquid crystal surfaces by X-ray and neutron scattering ». Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388101.
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Haire, Lesley Findlay. « Strategies for protein crystal growth-screening and optimization ». Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243778.
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Atkins, Alison J. « Solid state studies of ternary oxides and sulphides ». Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320791.
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McDowell, John Christopher. « Preparation characterisation and stability of selected high critical temperature ceramic superconductors ». Thesis, University of Ulster, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260854.
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Huang, Pao-Cheng. « Analysis of single-crystal semiconductor thin film structure by x-ray diffraction ». Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/20145.
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Butterworth, Susanna. « Single crystal X-ray diffraction studies on small, medium and large molecules ». Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5352/.
Texte intégralRésumé :
Chapter 1. Production of crystals for diffraction analysis would be assisted by the devising of a set of rules which, given molecular formula, could predict crystal formation conditions. By studying trends in structural properties of a group of closely related simple molecules, deductions could be drawn which could then be applied more generally. Chalcone derivatives with minor substituent differences were recrystallised. X-ray diffraction data collected and the structures solved and refined. Additionally, NMR and UV studies were performed, investigating an observed dimerisation reaction. Chapter 2. Discovery of peptide hormones and neurotransmitters has stimulated the study of structure-activity relationships, although the structure of these molecules is often poorly defined. Proctolin, a linear pentapeptide, is a neurotransmitter in insects. Crystallisation was attempted, with the aim of deducing the active conformation structure, thereby assisting in design of small molecule analogues for use as non-cholinergic pesticides. No diffraction was observed from the crystals produced. Chapter 3. Glucosamine 6-phosphate synthase is an N-terminal nucleophile amidotransferase catalysing the first step in the hexosamine pathway, from which all amino-sugar containing macromolecules are derived. Structure determination of each of two subdomains was attempted. In one case, pseudo-symmetry appeared to obstruct structure solution. The symmetry has subsequently been understood and the structure obtained. Crystals of the second domain are rotationally disordered. Chapters 4 and 5. Recent advances in macromolecular crystallographic techniques have facilitated the collection of an increasing number of high quality, atomic resolution data sets. Methods for refinement, previously limited to small molecule structures, have increasing relevance for proteins. Atomic resolution refinements using these evolving protocols have been performed on two small proteins, rubredoxin from Desulfovibrio vulgaris and the protein G immunoglobulin-binding domain. Appropriate treatment of the solvent structure in a protein crystal and the benefit to be gained by using sharpened density maps during refinement were investigated.
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Todd, Alan Kenneth. « Single crystal X ray diffraction studies of DNA and DNA drug complexes ». Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270250.
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Mohamed, Zakiah. « Relationships Among Structure, Magnetism and State of Charge in Positive Electrode Materials for Metal-Ion Batteries ». Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14438.
Texte intégralRésumé :
Polyanionic framework materials containing 3d transition metals such as iron, cobalt and manganese are attractive candidates as electrodes in lithium and sodium ion batteries due to their thermal stability, long cycle life and environmental friendliness. LiFePO4 is already used in some commercial lithium ion batteries as a positive electrode material where these are key attributes, but it still has lower energy density and higher costs compared to the more commonly used LiCoO2. This thesis describes a combined physical properties and magnetic structures some of these materials, aimed at improving our understanding of their solid-state chemistry, and ultimately their performance as battery materials by relating those physical and magnetic properties to the state of charge of the battery. A variety of polyanionic materials including phosphates, pyrophosphates and silicates were prepared using solid-state synthesis. All compounds were intensively characterized using specific heat capacity and magnetic measurements, X-ray, neutron and synchrotron X-ray diffraction techniques. Low-temperature neutron diffraction was used to solved and refined the magnetic structures. During the lithium extraction process, the magnetic properties can vary significantly because it involve redox reaction of transition metals. Measuring the magnetic properties of working electrode materials can therefore potentially provide information about local structural changes including the introduction of defects, decomposition and phase segregation. The magnetic properties of chemically delithiated samples were also studied so that they could be used as reference materials. In the first part of the thesis, the phosphates family AM1-xM′xPO4 (A = Li, Na; M = Mn, Fe; M′ = Zn, Mn, Fe) are intensively studied. These phosphates are modified in two ways: by doping with magnetic and non-magnetic transition metals. It was found that all compounds exhibit antiferromagnetic ordering at low temperatures, but the nature and ordering temperatures depend on doping. In the course of this work, the magnetic structures of two types of sodium phosphate were determined for the first time,triphylite and maricite NaFePO4. The triphylite type showed similar crystal and magnetic properties as LiFePO4, while the maricite type demonstrated a transition from commensurate (T < 12 K) to incommensurate (12 < T < 13 K) magnetic phases. A spin-flop transition in the commensurate phase was also observed. These results are discussed in the context of spin frustration on the Fe2+ sites. The second type of cathode material studied was the pyrophosphate A2M1-xM′xP2O7 (A = Li, Na; M = Fe; M′ = Co, Mn). Varying the compositions of these materials led to significant changes in crystallographic and electronic structure with remarkable effects on the magnetic properties and structures.The magnetic structures of Li2(Fe1-xCox)P2O7 and Na2(Fe1-xMnx)P2O7 solid solutions were explored in the course of this work. The crystal and magnetic structures of the silicates γ-Li2MnSiO4 and β-Li2CoSiO4 were investigated and their magnetic structures solved for the first time, including for chemically delithiated versions of Li2CoSiO4. Magnetic property measurements confirmed that Co had oxidised from Co2+ to Co3+, confirming that delithiation was successful while also serving to demonstrate the sensitivity of magnetic measurements to lithium content. In addition, the structural evolution of Li2CoSiO4 was tracked by in situ S-XRD and revealed no phase transformation during cycling. In summary, the outcome of this study is an extension of the state of knowledge of the low-temperature magnetic properties and structures of polyanion-based transition metal oxides, and a demonstration of the sensitivity of those properties and structures to electrochemical state. Further refinement of this approach could lead to a new tool for developing improved positive electrode materials for rechargeable batteries. The work also yielded crucial missing information concerning the electronic ground state of these materials, required for future high-level computational studies aimed at predicting properties including ionic conductivity.
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Bette, Sebastian. « Über basische Chloride des Nickel(II) und Magnesiums : Strukturen, Phasenbildung und Löslichkeit ». Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-207718.
Texte intégralRésumé :
In der vorliegenden Arbeit wurde die Phasenbildung im ternären System Ni(OH)2-NiCl2-H2O systematisch untersucht. Die basischen Nickel(II)-chlorid Phasen NiCl(OH), Ni2Cl(OH)3, NiClx(OH)2-x, Ni3Cl2+x(OH)4-x ∙ 2 H2O mit x = 0,26; 0,48; 0,82 und Ni3Cl2+x(OH)4-x ∙ 4 H2O mit x = 0,10 konnten phasenrein hergestellt und deren Kristallstrukturen mittels hochauflösender Röntgenpulverdiffraktometrie aufgeklärt werden. Die so erhaltenen strukturellen Daten wurden durch Anwendung von IR-und Spektroskopie, UV/VIS-Spektroskopie, SQUID-Messungen, Thermoanalysen und temperaturaufgelöster in-situ Röntgenpulverdiffraktometrie als komplementäre Methoden bestätigt. Weiterhin konnte eine allgemein anwendbare Routine zur Beschreibung der Diffraktionseffekte stapelfehlerbehafteter Schichtverbindungen für das Programm TOPAS entwickelt werden. Die Bildung und Stabilität der basischen Nickel(II)-chlorid Phasen in wässriger Nickel(II)-chlorid Lösung wurde systematisch bei 200°C und 25°C über Zeiträume von zwei Jahren untersucht und Löslichkeitsdaten ermittelt.
Des Weiteren erfolgte die Untersuchung der Wechselwirkung von Magnesium Oxid und basischen Magnesiumchlorid Phasen mit wässrigen nickelhaltigen Magnesiumchlorid Lösungen. Hierbei konnte die Mischkristallbildung zwischen analogen basischen Magnesium- und Nickel(II)-chloridphasen beobachtet werden. Es wurde festgestellt, dass basische Magnesiumchloride und Magnesiumoxid ein gutes Rückhaltevermögen für gelöstes Nickel aufweisen und dass ein Zutritt von gelöstem Nickel weder die Pufferwirkung noch die Beständigkeit der basischen Magnesiumchlorid Phasen beeinträchtigt.
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Edwards, Clare M. « Applications of high-pressure spectroscopic and powder x-ray diffraction techniques to inorganic materials ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0005/NQ44419.pdf.
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Edwards, Clare M. « Application of high-pressure spectroscopic and powder X-ray diffraction techniques to inorganic materials ». Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37544.
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The vibrational spectra (IR, Raman) of (eta6-C 6H5CO2CH3)Cr(CO)3, (eta 6-C6H5CO2CH3)Cr(CO) 2(CS), [Pt(NH3)4][PtCl4] (MGS), [Pt(ND 3)4] [PtCl4] (MGS-D), [Pt(NH 3)4][PtBr4] (MGS-Br), ReH7(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane) and CpCo(C64H4) (Cp = cyclopentadiene) have been studied under pressures up to ∼45 kbar. The magnitude and direction of the pressure-induced shift of the Raman-active nu(CO) and nu(CS) vibrational modes of (eta6-C6H 5CO2CH3)Cr(CO)3 and (eta6 -C6H5CO2CH3)Cr(CO) 2(CS) indicate an increase in the amount of pi-backbonding to the CO and CS ligands, under pressure, the increase being greater to the CO ligand than to the CS ligand. Wavenumber vs. pressure plots revealed a phase transition in both the tricarbonyl and thiocarbonyl complexes between 10--15 kbar. For CpCo(C64H4), discontinuities in the wavenumber vs. pressure plots at 10 kbar indicate a phase transition at this pressure, most likely involving rotation of the Cp ring. Insertion of the Co atom into the cage does not occur under compression; a shift to higher wavenumbers was observed for all the Raman and IR vibrational modes of CpCo(C64H4) and the parent fulleride, C 64H4. Phenyl ring rotation is thought to occur in ReH 7(dppe) under compression. Three pressure regions, from ambient pressure to ∼16 kbar, between 16 and 29 kbar and above 29 kbar, were identified from the wavenumber vs. pressure plots. A broad, weak feature in the ER spectrum appears from 5 kbar, increasing in intensity with increasing pressure. This peak has been assigned to the nu(HH) mode of a coordinated dihydrogen ligand, Re(eta2-H2). Ring rotation may assist the pressure-induced dihydride-dihydrogen interconversion. The pressure-tuning IR study of MGS and its derivatives probed the intermolecular interactions, in particular the interactions of the NH3 groups and investigated the hypothesis that hydrogen bonding of the type N- H&cdots;Cl exists in MGS. Splitting of the IR bands at ambient pressure, and