This thesis deals with the current methods available for X-ray structure determination and with the crystal and molecular structure determination of five compounds using these methods. The five compounds are 1) [ 2,3-Bis (dimethylarsino)- 1, 1, 1,4, 4, 4-hexaf luorobut-2-ene-As,As]tricarbonyldiiodotungsten(II),Me₂AsC (CF₃):C (CF₃) AsMe₂WI₂(CO)₃ 2) Dimethylammonium trichlorotris(dimethylsulphoxide}-ruthenate(II) , [ ( (CE₃)₂ SQ)₃ RuCl₃ ]⁻ [ (CH₃)₂ NH ₂]+ 3) Dichlorotetrakis{dimethylsulphoxide)ruthenium(II), (Me₂SO)₄fRuCl₂ 4) 1,3,7-Triraethyl-2,6-dioxypuriae hydrochloride dihydrate (caffeine hydrochloride dihydrate), CH₁₁C1N₄0₂-2H₂0 .5) 1-Acetyl-3-benzamido-2-keto-4- (2,3, 4, 6-tetra-O-acetyl-β-D-glucopyranosyloxy)-Δ³-pyrroline, C ₂₇H₃₀N₂O₁₃ The structures of compounds 1), 2), and 3) were determined by Patterson syntheses, compound 4) by centrosymmetric direct methods and compound 5) by non-centrosymmetric direct methods. All structures were then refined using full-matrix least-sguares procedures. The relevant crystal data for all five compounds can be found in Table A In the tungsten compound [1) the tungsten atom is seven-coordinate with a distorted capped octahedral environment, the capping group being a carbonyl. The capped face consists of the two remaining carbonyl groups and one of the arsenic atoms from the bidentate ligand. The uncapped face contains the two iodine atoms and the remaining arsenic. Crystal data for the five compounds examined atom. The structure of the ruthenium compound [ 2) ] consists of two crystallcgraphically non-equivalent anions in the asymmetric unit linked by hydrogen bonding via dimethylammonium cations. The coordination geometry about the structurally similar anions is essentially that of an octahedron with the DHSO ligands being bonded to Ru via the sulphur atoms. The co-ordination geometry about the ruthenium atom for compound 3) is essentially octahedral with cis chlorine atoms; Of the four DMSO ligands three are S-bonded and one is O-bonded, the O-bonded ligand being trans to a S-bonded ligand. For caffeine hydrochloride [ 4) ] the fused ring system is essentially planar and protonated at the 9-positioh. The crystal contains two types of hydrogen bonding involving 0-H...C1 and N-H...0 interactions. The structure of compound 5) consists of a pyranose ring in the chair conformation with the four 0-acetyl substituents in equatorial positions; the pyranose ring is connected to a planar pyrroline ring via a β-oxygen bridge. / Science, Faculty of / Chemistry, Department of / Graduate

The aim of this thesis was to examine materials using high resolution X-ray diffraction techniques. Initial work involved the synthesis of various metal phosphates to investigate their suitability for charge density work. Many of these were discovered to be of insufficient quality for further study. Much of the phosphate synthesis work performed at the moment utilises an ionic liquid both as a solvent and structure directing agent which dictates the topology of the structure due to its size and charge density. As such the ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate used in the synthesis process was examined with high resolution X-ray diffraction as it was possible to produce large pure crystals which could be examined further. A high resolution data set was also collected from the metal organic framework SIMOF-1 which produced a preliminary multipole model however further data collections are required to improve the quality of the model. A multi-technique investigation involving X-ray diffraction, solid state NMR and first principles calculations was carried out on the aluminophosphate material AlPO₄-15. A synchrotron X-ray single crystal diffraction study was carried out on the same sample as that used in solid state NMR studies. The model from the single crystal study, together with a model from a literature high resolution study of the same material, were used as starting points for the first-principles calculations of the NMR parameters. This enabled the ³¹P and ²⁷Al NMR spectra to be unambiguously assigned and all the NMR parameters calculated agreed well with the experimental spectra even without relaxing the X-ray derived structural models. Highlighting that as long as a good data set has been collected in the first place the atomic positions would not change too drastically. Other aspects of this thesis involved investigations into other ionothermally prepared systems such as the use of different phosphonate sources to provide functionality to the materials. This work resulted in some interesting findings such as the ionic liquid breaking down and being incorporated into the framework via the metal. Many of the structures produced were of a layered nature however a molecular structure was also synthesised which is unlike the vast majority of hydrothermally prepared phosphonates, which are layered. The negligible vapour pressure provided by the ionic liquid has enabled synthesis reactions to be investigated with glass vessels on an energy dispersive beam line. This work highlighted how it is possible to study the synthesis process in-situ and compare microwave assisted reactions against a conventional heating method, the results indicate that two different types of reactions are occurring resulting in different intermediates which is due to the way the reagents are heated. The microwave assisted reactions also result in larger purer crystals which highlights the importance of the method in materials synthesis. The use of a specially designed environmental gas cell was used to investigate the adsorption properties of the metal organic framework CPO-27-Co in-situ. Using the cell it was possible to locate sulfur dioxide physisorbed and chemisorbed sites with in the framework which could be removed by the application of a vacuum and heat. It was also possible to locate the chemisorbed sites for nitric oxide within the metal organic framework however due to the low scattering factor and disorder from the gas it was not possible to locate the physisorbed sites.

M.Sc. / Aspects of electron-electron correlations have for the past few decades been at the forefront of research in Solid State Physics. More traditional concepts under this topic have been phenomena such as superconductivity, and magnetic ordering in its many forms including long-range ordering and spin-glass freezing. The class of so-called strongly correlated electron systems has been a particularly active field of study, as witnessed by for instance the series of annual international conferences held under this topic since 1992. Compounds and alloys of strong electronic correlations have proved a very rich field of new and anomalous physical behaviours in metallic and semiconducting compounds and alloys of especially 4f- and 5f-electron systems, together with ceramics characterized as the so-called ¡§high-TC¡¨ superconductors. The f-electron systems have revealed a variety of behaviours such as ~ 1000-fold enhanced effective electron masses at low temperature, coexistence of superconductivity and magnetic ordering in systems where the magnetic interactions are far too strong to allow for Cooper-pair formation within the well-established BCS-interpretation, and electron transport and thermodynamic behaviour at low temperatures that completely defy our conventional Fermi-liquid paradigm of understanding the ground states of metals. The series of pseudo-ternary compounds Ce1-xLaxRu4Sn6 that were synthesized and characterized in this work for the first time are formed by substituting La for Ce in CeRu4Sn6, the parent compound. CeRu4Sn6 exhibits a number of properties which have been associated with a special class, the Kondo semiconductors of strongly correlated electron systems. CeRu4Sn6 has very recently been shown [A. M. Strydom et al. (2004)] to comprise an intriguing combination of characteristics that are thus far unique among the Kondo semiconductors: At low temperature (T 10 K) the specific heat proves the development of very strong electronic correlation out of an already low density of charge carriers (as shown by Hall-effect, resistivity, and the Sommerfeld coefficient of the specific heat). Furthermore, the specific heat follows a logarithmic increase as temperature is decreased below ~ 2 K, in a range where thermal transport shows the presence of an energy gap in the electronic density of states. The aim of this work was to investigate the intermediate and higher temperature (4.01 K „T T „T 300 K) behaviour of the electrical resistivity of the Ce1-xLaxRu4Sn6 series of compounds in which the concentration of the 4f-electron magnetic ion Ce is progressively being reduced. A steady but slow decrease of the energy gap with increasing La concentration was found in this work in contrast with what is usually the case in Kondo semiconductors. Both the presence of an energy gap and the low density of charge carriers are found to be connected to the presence of Ce in the unit cell, and are therefore not an artefact of the peculiar filledƒ{cageƒ{like tetragonal crystal structure of these compounds. An interesting strong anisotropy was found in the way in which the tetragonal unit cell expands preferentially within the aƒ{b plane, compared to the elongation along the cƒ{axis, upon moving from CeRu4Sn6 to LaRu4Sn6. / Prof. A.M. Strydom

by Andreas Kyriacou. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web. / The effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder x-ray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the Fe-HAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5-x)Fex(PO4)3OH with 0< x < 0.3 were prepared. Single phase HAp was identified in x-ray diffraction patterns (XRD) of samples with x < 0.1 inferring that the solubility limits are less than 0.1. Hematite ((Sa(B-Fe2O3) is identified as a secondary phase for higher Fe content. The refined parameters show that Fe is incorporated in the HAp structure by replacing Ca in the two crystallographic sites with a preference at the Ca2 site. This preference explains the small effect of the Fe substitution on the lattice constants of HAp. The overall decrease of the lattice constants is explained by the ionic vi size difference of Ca and Fe. The increasing trend of the a-lattice constant with x in the Fe substituted samples is attributed to a lattice relaxation caused by the substitution of the 4- and 6-fold Fe at the 7- and 9-fold Ca1 and Ca2 sites. This Ca local geometry reduction is indicated by a slight increase of the Ca1-O3 and Ca2-O1 bond lengths. Above the solubility limit x = 0.05, the Fe is partitioned in and out of the HAp structure with increasing nominal Fe content x. The excess Fe is oxidized to hematite. The TEM analysis and magnetic measurements support the results of the simultaneous Rietveld refinements. The TEM images show no significant effect on the morphology and size of the HAp particles upon Fe incorporation. The particles are either spheres or short rods of dimensions 20-60 nm. Hematite particles are imaged in the samples with x exceeding the solubility limit. These particles

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016. / Inclusion compounds of two hydroxyl hosts with a variety of guests have been investigated. These host compounds are bulky molecules and have the ability to interact with smaller organic guests to form new compounds. The host 9-(1-naphthyl)-9H-xanthen-9-ol (H1), forms inclusion compounds with pyridine (PYR), N,N-dimethylacetamide (DMA), morpholine (MORP) and N-methyl-2-pyrrolidinone (NMP). The crystal structures of H1•NMP, H1•DMA and H1•MORP1 were successfully solved in the triclinic space group PĪ, whereas the inclusion compound H1•PYR crystallised in the monoclinic space group P21/c. A different inclusion compound involving morpholine, H1•MORP2 resulted from dissolution of H1 in a 1:1 molar ratio of MORP: DMA. H1•MORP2 crystallised in the space group PĪ. All of the abovementioned inclusion compounds demonstrated a host: guest ratio of 1:1 except for H1•MORP1 (host: guest ratio = 1: ). H1 interacts with pyridine and morpholine guests via (Host)O-H•••N(Guest) hydrogen bonds and via (Host)OH•••O(Guest) hydrogen bonds with N-methyl-2-pyrrolidinone and N,N-dimethylacetamide.

Iu Kwan Sai = 以光致發光譜和高解析度X射線衍射譜研究砷銻化鎵外延層和量子井 / 姚昀樨. / On t.p. "̳x" is subscript. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 93-95). / Text in English; abstracts in English and Chinese. / Iu Kwan Sai = Yi guang zhi fa guang pu he gao jie xi du X she xian yan she pu yan jiu shen ti hua jia wai yan ceng he liang zi jing / Yao Yunxi. / ACKNOWLEDGMENTS --- p.i / ABSTRACT --- p.ii / TABLE OF CONTENTS --- p.v / LIST OF TABLES --- p.vii / LIST OF FIGURES --- p.viii / Chapter 1. --- INTRODUTION --- p.1 / Chapter 1.1 --- Motivations --- p.1 / Chapter 1.2 --- Historical Works --- p.1 / Chapter 1.3 --- This Study --- p.3 / Chapter 1.4 --- Growth Conditions of GaAs1-xSbx Alloy --- p.4 / Chapter 2. --- EXPERIMENTAL PROCEDURES --- p.5 / Chapter 2.1 --- High Resolution X-Ray Diffraction (HRXRD) --- p.5 / Chapter 2.1.1 --- The Use of HRXRD --- p.5 / Chapter 2.1.2 --- Setup of the High Resolution X-Ray Diffractometer --- p.7 / Chapter 2.1.3 --- Types of Measurements --- p.8 / Chapter 2.2 --- Photoluminescence (PL) Spectrometer --- p.10 / Chapter 2.2.1 --- The Use of PL --- p.10 / Chapter 2.2.2 --- Setup of PL spectrometer --- p.10 / Chapter 2.2.3 --- types of Measurements --- p.13 / Chapter 3. --- CHARACTERIZATION --- p.14 / Chapter 3.1 --- High Resolution X-Ray Diffraction (HRXRD) --- p.14 / Chapter 3.1.1 --- Principal Scattering Geometries --- p.14 / Chapter 3.1.2 --- Strains in the Epitaxial Layer --- p.16 / Chapter 3.1.3 --- Lattice Parameter --- p.21 / Chapter 3.1.4 --- Sb Composition --- p.24 / Chapter 3.1.5 --- Determination of Thickness --- p.24 / Chapter 3.2 --- Photoluminescence (PL) --- p.25 / Chapter 3.2.1 --- Basic Theory of PL --- p.25 / Chapter 3.2.2 --- Strain and Temperature Effect --- p.26 / Chapter 3.2.3 --- Type I and Type II PL --- p.27 / Chapter 3.2.4 --- The Energy Gap of GaAs1-xSbx --- p.28 / Chapter 4. --- RESULTS AND DISCUSSION --- p.31 / Chapter 4.1 --- Direct Analysis of HRXRD Rocking Curves --- p.31 / Chapter 4.1.1 --- GaAs1-xSbx / GaAs Quantum Wells (QWs) --- p.31 / Chapter 4.1.2 --- GaAs1-xSbx /InP Epitaxial Layers --- p.42 / Chapter 4.2 --- Computer Simulation of HRXRD --- p.51 / Chapter 4.2.1 --- Simulation Theory --- p.51 / Chapter 4.2.2 --- Simulation of Rocking Curves --- p.51 / Chapter 4.3 --- Room Temperature PL of GAAs1-xSBx Quantum Wells and Epitaxial Layers --- p.66 / Chapter 4.4 --- Low Temperature (LT) PL of GAAs1-xSBx Quantum Wells and Epitaxial Layers --- p.75 / Chapter 4.5 --- Excitation Power Dependent (PD) PL of GAAs1-xSBx Quantum Wells and Epitaxial Layers --- p.78 / Chapter 4.6 --- Temperature Dependent (TD) PL of GAAs1-xSBx Quantum Wells and Epitaxial Layers --- p.85 / Chapter 5. --- CONCLUSIONS --- p.90 / REFERENCES --- p.93

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Chancey, Ryan / text