This thesis describes a study of the low temperature specific heat of LiⅹNbS₂, where x is between 0 and 1. Samples were prepared by intercalating lithium into niobium disulfide in electrochemical cells. Structural data obtained by x-ray diffraction are presented. These, together with electrochemical measurements, show that staged phases exist for some values of x. The electronic specific heat of LiⅹNbS₂, is consistent with complete charge transfer from the intercalated lithium to the bands of the NbS2 host. The lattice specific heat also shows large changes as a function of x. A discussion of the data in terms of continuum elasticity theory suggests that intercalation produces large changes in the shear elastic constant C₄₄ . A brief discussion of superconductivity in LiⅹNbS₂, is also included. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

We have elucidated the structures of a series of Werner Clathrates with systematically changing guest molecules. The host is the inorganic coordination compound bis(isothiocyanato)tetra(4-vinylpyridine)nickel(II), [Ni(NCS)2(4-ViPy)4]. The guests are mixtures of tetrahydrofuran and the cyclic hydrocarbons: cyclohexane, cyclohexene, 1,3-cYclohexadiene, 1,4-cyclohexadiene and benzene. Host to guest ratios were elucidated by density and proton nuclear magnetic resonance spectroscopy. The thermal characteristics of the compounds were analysed by thermogravimetric analysis and differen.tial thermal analysis. The structures of two related compounds [Ni(NCS)2(Py)4] and [Ni(NCS)2(Py)4].nbenzene were also studied.

Includes bibliographical references. / The crystal structures of trans-9, 10-dihydroxy-9, 10-diphenyl-9, 10- dihydroanthracene with various guest molecules have been determined by X-ray diffraction. The guests were 2-butanone, 4-vinylpyridine, 4-methylpyridine and 2-methylpyridine. The host to guest ratios were determined by microanalysis and density measurements. The change of the overall host lattice structure upon guest release was studied by X-ray powder diffraction. The thermal characteristics of the compounds were studied using thermogravimetric analysis and differential scanning calorimetry. Guest desorption from three of the four compounds occurred in a single step whereupon the host framework collapsed back to the guest-free structure. The compound containing 4-methylpyridine, released the guest molecules in a two-step process. Evidence of a new host phase was identified from the XRD pattern of this intermediate phase. On further guest release, the intermediate phase converted to the guest-free host structure. In an attempt to reconcile thermodynamics with structure, the correlation between hydrogen bond length and guest desorption enthalpy was investigated.

by Yuet-ming Man. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 49-52.

by Chi-Keung Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 100-103). / Abstract also in Chinese. / Acknowledgments --- p.i / Abstract --- p.ii / 摘要 --- p.iii / Table of contents --- p.iv / Index of compounds --- p.v / List of tables --- p.vi / List of figures --- p.vii / Chapter Chapter 1. --- Introduction / Chapter 1.1 --- Some aspects of urea/thiourea inclusion chemistry --- p.1 / Chapter 1.2 --- General chemistry of monocyclic oxocarbons --- p.5 / Chapter 1.2.1 --- Synthesis of monocyclic oxocarbons --- p.5 / Chapter 1.2.2 --- Aromaticity of monocyclic oxocarbon anions --- p.20 / Chapter 1.2.3 --- Reactions of monocyclic oxocarbons --- p.25 / Chapter 1.3 --- Aim of the present research --- p.31 / Chapter Chapter 2. --- Description of crystal structures / Chapter 2.1 --- Urea-anion inclusion compounds --- p.32 / Chapter 2.1.1 --- Bis(tetra-n-propylammonium) squarate-urea-water (1/ 6/2) --- p.32 / Chapter 2.1.2 --- Tetra-n-butylammonium hydrogen squarate-urea-water (1/1/1) --- p.38 / Chapter 2.1.3 --- Bis(tetraethylammonium) squarate-tetraethylammonium hydrogen carbonate- urea-water (1/2/4/6) --- p.42 / Chapter 2.1.4 --- Bis(tetra-n-propylammonium) croconate-urea-water (1/5/2) --- p.47 / Chapter 2.2 --- Thiourea-anion inclusion compounds --- p.53 / Chapter 2.2.1 --- Bis(tetraethylammonium) squarate-thiourea-water (1/4/ 2) --- p.53 / Chapter 2.2.2 --- Bis(tetraethylammonium) squarate-thiourea (1/6) --- p.59 / Chapter 2.2.3 --- Bis(tetra-n-propylammonium) squarate-thiourea-water (1/ 4/2) --- p.66 / Chapter Chapter 3. --- Summary and discussion / Chapter 3.1 --- Urea/thiourea monocyclic oxocarbon anions inclusion compounds --- p.71 / Chapter 3.2 --- Structural features and topological correlations of the host lattices --- p.72 / Chapter 3.3 --- Hydrogen bonding and linkage modes of urea and thiourea molecules --- p.87 / Chapter Chapter 4. --- Experimental / Chapter 4.1 --- Preparation of crystals --- p.91 / Chapter 4.2 --- X-ray Crystallography --- p.93 / References --- p.100 / Appendix Atomic coordinates and thermal parameters of the new inclusion compounds --- p.104

No description available.

Thesis (Ph.D.)--Tufts University, 1999. / Adviser: Terry Haas. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

The vibrations of H₂O, HDO and D₂O molecules participating in the hydrogen bonding of vitreous and crystalline solids, and some alkyl halides and halogens encaged in these solids, were studied by infrared spectroscopy between 4.2 and 200°K over the 4000 to l60 cm⁻¹ frequency range. Four kinds of 0-H‧‧‧‧0 hydrogen bonding lattices were investigated, vitreous and annealed (cubic) ice I and vitreous and annealed clathrate-hydrate mixtures. In vitreous ice I the effects on the molecular and lattice vibrations were observed in detail for H₂O between 77 and l80°K during the phase transformation to cubic ice I, and the results of the transformation for HDO and D₂O were recorded. As well, the effects on the molecular and lattice vibrations of H₂0, D₂0, H₂0 (5-9W HDO), and D₂0 (4.00% HDO) cubic ices I were studied during warming from 4.2 to 200°K. Similar studies were made for the vibrations of H₂0, HDO, D₂0 and guest molecules, during the vitreous-crystalline phase transformation of seven clathrate-hydrate mixtures and during warming of the resulting annealed mixtures. For ice I the method involved condensation of the vapour at 77°K, observation of the spectra during warming in stages to 185 ± 5°K, cooling to 4.2°K, and observation of the cubic sample spectra during warming to 200°K. The results were plotted as a function of temperature and were correlated to calculated distances and RMS amplitudes of translation. As well four models for molecular libration were investigated. Three approaches were taken to the clathrate-hydrate problem. In parallel to the ice I method gaseous stoichiometric mixtures were condensed, observed during transformation, cooled to 4.2°K and observed during warm-up. Other gaseous clathrate mixtures were condensed in an isolated sample chamber, to prevent sample fractionation, and treated as before. Finally, low temperature mulls of solid clathrate-hydrate mixtures were prepared and observed at 83 ± 3°K. The results show that on warming the ice I phase transformation occurred between 120 ± 5 and 135 ± 5°K and required, less than 18 minutes at 135 ± 3°K. Weak peaks due to oligomeric H₂O and D₂O units disappeared during annealing, while all hydrogen bonded H₂O molecular modes shifted to lower frequency and all lattice modes shifted to higher frequency. The half-height widths of the composite H₂O band (v₂/2vR) appeared to increase upon annealing and to decrease upon warming while the (VR, VR + vT) and (v₁, v₃, v₁ + vT) bands had the opposite behaviour. This was interpreted, as indicating a weak 2vR band underlying the stronger v₂ absorption near 1600 cm⁻¹. The frequency-temperature dependences of all cubic ice I bands were interpreted on a bilinear, high and low temperature basis (the lattice modes shifted to lower frequency and the molecular modes to higher frequency with increasing temperature). For HDO above 86°K [formula omitted] was 0.200 ± 0.005 cm⁻¹/°K, [formula omitted] was 0.123 ± 0.005 cm⁻¹/°K, the frequencies were "frozen-in" at 80 ± 5°K and 65 ± 5°K and had irregular behaviours between 50 and 70°K. The low temperature dependences were 0.047 ± 0.005 cm⁻¹/°K in both modes. An explanation is given for the apparent displacement of the HDO stretching frequencies from the H₂O and D₂O frequencies. The HDO results also permitted the accurate determination of [formula omitted] as 1921 cm⁻¹/Å and [formula omitted] as 128l cm⁻¹/Å above 150°K and as 8202 cm⁻¹/Å and 6629 cm⁻¹/Å below 100°K. As well, the HDO stretching frequencies gave an anharmonicity which increased from 4.2 to 80°K and then decreased between 80 and 200°K. The clathrate-hydrate mixtures transformed on warming in the temperature range 125 ± 5 to 145 ± 5°K and required less than l8 minutes at 135°K as for ice I. Similarly, the weak oligomeric and guest absorptions disappeared upon annealing. From the comparison of the three sets of "clathrate" results and the behaviour of annealed sample peaks we concluded that cubic ice I and not clathrate-hydrate was probably formed. / Science, Faculty of / Chemistry, Department of / Graduate

The Li-Ti-S ternary system was investigated. The elements and/or compounds, such as lithium sulfide, titanium disulfide and titanium trisulfide, were combined at high temperature (typically 500-900°C). The synthesized compounds containing one or more phases were structurally characterized using x-ray powder diffraction. When Lix TiS₂, (0 ≤ x ≤ 1) was synthesized at elevated temperature, a new polytype, 3R-LixTiS₂, was found for some values of x. The regions of stability of the 3R polytype and the well known 1T polytype are presented. Lithium can be intercalated or de-intercalated from both polytypes at room temperature. Ambient temperature Li/3R-LixTiS₂ cells have higher average voltages than Li/1T-Li TiS₂, cells. The lithium spinel oxides are another class of materials receiving attention as cathode materials in lithium secondary batteries. LiTi₂0₄ is metallic, has the cubic spinel structure and reacts with one further lithium atom to form Li₂Ti₂0₄. The related spinel Li₄/₃Ti₅/₃⁰₄͵ which is electrically insulating, also reacts reversibly with one lithium atom. Both Li₂Ti₂0₄ and Li₄/₃Ti₅/₃⁰₄͵ cells cycle reversibly, but have subtle differences in their voltage profiles. The difference in cell behaviour was interpreted based on the band structure of Li₁˖xTi₂₋x⁰₄. The mixed spinels LiMnyTi₂₋y⁰₄ (0 ≤ y ≤ 2) were also investigated. These compounds were synthesized at high temperature but their performance as cathodes in lithium batteries was not encouraging. / Science, Faculty of / Physics and Astronomy, Department of / Graduate