Made available in DSpace on 2014-10-09T12:23:44Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:48Z (GMT). No. of bitstreams: 1 00947.pdf: 5792768 bytes, checksum: 3655a803616339af18a1a368dc3f4567 (MD5) / Thesis / IEA/T / University of Sussex, England

Energias de ligação do estado fundamental de doadores rasos em super-redes são consideradas teoricamente com o auxílio de um procedimento variacional que leva em conta a mistura do contínuo de estados da minibanda à qual o mesmo está associado. Os cálculos são realizados para um grande número de parâmetros de super-rede e qualquer posição da impureza na mesma. É mostrado que a dependência da energia de ligação com os vários parâmetros envolvidos pode ser completamente explicada em termos de um modelo simples unidimensional (tight-binding) onde a largura da respectiva minibanda de condução e a energia de ligação no Limite de poço isolado são os únicos parâmetros relevantes. A extrema concordância quantitativa entre as energias de ligação derivadas deste modelo e as obtidas pelo método variacional mais rigoroso vem enfatizar o papel fundamental desempenhado pela largura de minibanda com o único parâmetro relevante ao se levar em conta os efeitos de tunelamento existentes nas super-redes. / A variational procedure which takes into account the mixing of a continuum of subband states has been used to investigate the binding energies of shallow donors in superlattices. The calculations where performed for a wide range of superlattices parameters and impurity positions. It is shown that the dependence of the binding energy upon the various superlattice parameters can be completely explained in terms of a simple onedimensional tight-binding model where the bandwidth of the respective conduction subband and the binding energy in the isolated quantum well are the only relevant parameters. The quantitative overall agreement between the binding energies derived from this model and those found variationally is excellent and emphasizes the fundamental role played by the bandwidth as the only relevant parameter accounting for the tunneling effects.

Made available in DSpace on 2014-10-09T12:23:44Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:48Z (GMT). No. of bitstreams: 1 00947.pdf: 5792768 bytes, checksum: 3655a803616339af18a1a368dc3f4567 (MD5) / Thesis / IEA/T / University of Sussex, England

Um estudo teórico detalhado das estruturas e energias do ligante 1, 7, 11, 17-tetraoxa-2, 6, 12, 16-trazaocicloocsano ([20]aneN4O4) coordenado com íons metálicos de transição Fe2+, Co2+, Ni2+, Ru2+, Rh2+ e Pd2+ foi realizado em nível de teoria B3LYP/Lanl2DZ. As geometrias dos complexos foram totalmente otimizados em simetria Cs com os íons metálicos coordenados com quatro átomos de nitrogênio (complexos 1a e 1aq) ou quatro átomos de oxigênios (complexos 1b e 1bq) e duas moléculas de água. Os arranjos octaédricos (1a e 1b) e quadrado-planares (1aq e 1bq) foram consideremos neste trabalho. A estrutura teórica está em excelente acordo com a estrutura de difração de raio-x experimental determinada para o complexo octaédrico de Ni2+ de [20]AneN4O4. Os cátions M2+ ligam-se preferencialmente aos átomos de nitrogênios com energia de ligação que aumenta na ordem Fe2+ < Ru2+ < Co2+ < Ni2+ < Rh2+ < Pd2+. Para os metais de transição da primeira fila, os complexos de spin alto são mais estáveis que os complexos de spin baixo. Em contraste, para os metais de transição da segunda fila, os estados de spin baixo mostraram-se mais estáveis que os estados de spin alto. As ligações metal-ligante nos complexos foram analisadas em termo das interações covalentes e iônicas e ajudaram a entender porque os complexos (1a e 1aq) são mais estáveis que os complexos (1b e 1bq). Os complexos poliaminas [20]aneN4 e poliéteres [20]aneO4 foram obtidos substituindo os átomos de nitrogênio e oxigênio da posição alfa dos macrociclos [20]aneN4O4 e [20]aneO4N4, respectivamente. O macrociclo [20]aneO4 tem preferência em complexar íons metálicos da primeira fila, enquanto o macrociclo [20]aneN4 prefere complexar os íons metálicos da segunda fila. / A detailed theoretical study of structures and energies of the 1,7,1l,17-tetraoxa-2,6,12,16-tetraaza-cycloeicosane ligand ([20]AneN4O4) coordinated to Fe2+, Co2+, Ni2+, Ru2+, Rh2+ and Pd2+ transition metals ions was carried out with the B3LYP/Lanl2DZ method. The geometries of the complexes were fully optimized in Cs symmetry with the metal ions coordinated either to four atoms nitrogen (complexes 1a e 1b) or to the four atoms oxygen (complexes 1aq e 1bq). The octahedral and square planar arrangements were considered in this work. The theoretical structure is in excellent agreement with the experimental X-ray diffraction structure determination for the [20]AneN4O4 octahedral Ni2+ complex. The M2+ cations bind preferentially to the nitrogen atoms with binding energies that increase in the order Fe2+ < Ru2+ < Co2+ < Ni2+ < Rh2+ < Pd2+. For the first-row transition metals, the highspin complexes are more stable than the low-spin complexes. In contrast, for the second-row of transition metals, the low-spin states were found more stable than the high spin states. The metal-ligand bonds in the complexes were analyzed in terms of the covalent and ionic interactions and helped to understand why complexes (1a e 1aq) are more stable than complexes (1b e 1bq). The polyamines [20]aneN4 and polyethers [20]aneO4 complexes were obtained substituting the atoms N or O of the alfa position of the macrocycles [20]aneN4O4 and [20]aneO4N4, respectively. The macrocycle [20]aneO4 prefers to complex first-row transition metals; however, the macrocycle [20]aneN4 prefers to complex second-row transition metals.

No description available.

Indications that existing parameter sets of extended Linear Interaction Energy (LIE) models are transferable between lipases from Rhizomucor Miehei and Thermomyces Lanigunosus in complex with a small set of vinyl esters are demonstrated. By calculat- ing energy terms that represents the cost of forming cavities filled by the ligand and the complex we can add them to a LIE model with en established parameter set. The levels of precision attained will be comparable to those of an optimal fit. It is also demonstrated that the Molecular Mechanics/Poisson Boltzmann Surface Area (MM/PBSA) and Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) methods are in- applicable to the problem of calculating absolute binding energies, even when the largest source of variance has been reduced.

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第23586号 / エネ博第432号 / 新制||エネ||82(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 松田 一成, 教授 宮内 雄平 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

In this work, the Drift Tube Ion Mobility technique is used to study the hydrophobic hydration and solvation of organic ions and measure the thermochemistry and kinetics of ion-molecule reactions. Furthermore, an exploratory study of the intracluster polymerization of isoprene will be presented and discussed. The ion hydration study is focused on the C3H3+ cation1 and Pyridine▪+ radical cation.2 The chemistry of the cyclic C3H3+ cation1 has received considerable attention and continues to be an active area of research.3-7 The binding energies of the first 5 H2O molecules to c-C3H3+ were determined by equilibrium measurements. The measured binding energies of the hydrated clusters of 9-12 kcal/mol are typical of carbon-based CH+•••X hydrogen bonds. The ion solvation with the more polar CH3CN molecules results in stronger bonds consistent with the increased ion-dipole interaction. Ab initio calculations show that the lowest energy isomer of the c-C3H3+(H2O)4 cluster consists of a cyclic water tetramer interacting with the c-C3H3+ ion, which suggests the presence of orientational restraint of the water molecules consistent with the observed large entropy loss. The c-C3H3+ ion is deprotonated by 3 or more H2O molecules, driven energetically by the association of the solvent molecules to form strongly hydrogen bonded (H2O)nH+ clusters. The kinetics of the associative proton transfer (APT) reaction C3H3+ + nH2O → (H2O)nH+ + C3H2• exhibits an unusually steep negative temperature coefficient of k = cT(sup>63±4 (or activation energy of -32 ± 1 kcal mol-1). The behavior of the C3H3+/water system is exactly analogous to the benzene+• /water system8,9, suggesting that the mechanism, kinetics and large negative temperature coefficients may be general to multibody APT reactions. These reactions can become fast at low temperatures, allowing ionized polycyclic aromatics to initiate ice formation in cold astrochemical environments.The solvation energies of the pyridine•+ radical cation by 1- 4 H2O molecules are determined by equilibrium measurements in the drift cell. The binding energies of the pyridine•+(H2O)n clusters are similar to the binding energies of protonated pyridineH+(H2O)n clusters that involve NH+∙∙OH2 bonds, and different from those of the solvated radical benzene•+(H2O)n ions that involve CHδ+∙∙OH2 bonds. These relations indicate that the observed pyridine•+ ions have the distonic •C5H4NH+ structure that can form NH+∙∙OH2 bonds. The observed thermochemistry and ab initio calculations show that these bonds are not affected significantly by an unpaired electron at another site of the ion. The distonic structure is also consistent with the reactivity of pyridine•+ in H atom transfer, intra-cluster proton transfer and deprotonation reactions. The results present the first measured stepwise solvation energies of distonic ions, and demonstrate that cluster thermochemistry can identify distonic structures.The gas phase clustering of small molecules around the hydronium ion is of fundamental interest and is relevant to important atmospheric and astrophysical processes. In this work, the equilibrium constants for the formation of the H3O+(X)n clusters with X = H2, N2 and CO and n = 1-3 at different temperatures are measured using the drift tube technique10. The arrival time distributions (ATDs) of the injected H3O+ and the H3O+(X)n clusters formed inside the cell are measured under equilibrium conditions. The resulting binding energies for the addition of one and two hydrogen molecules are similar [3.4 and 3.5 kcal/mol, respectively). For the N2 clustering with n = 1-3, the measured binding energies are 7.9, 6.9 and 5.4 kcal/mol, respectively. The clustering of CO on the H3O+ ion exhibits a relatively strong binding energy (11.5 kcal/mol) consistent with the dipole moment and polarizability of the CO molecule. Theoretical calculations of the lowest energy structures are correlated to the experimental results. Finally, intracluster polymerization leading to the formation of covalent bonded oligomer ions has been investigated following the ionization of neutral isoprene clusters. The results indicate that isoprene dimer cation has a structure similar to that of the limonene radical cation. Mass-selected mobility and dissociation studies also indicate that the larger isoprene cluster ions have covalent bonded structures. The conversion of molecular clusters into size-selected oligomers is an important process not only for detailed understanding of the early stages of polymerization but also for practical applications such as the formation of new polymeric materials with controlled and unusual properties.

No description available.

Die Oberflächen-stoßinduzierte Fragmentierung von reinen und gemischten Antimonclustern wurde im Bereich hyperthermischer Kollisionsenergien untersucht. In diesem Energiebereich sind die Prozesse des Ladungstransfers, des Energietransfers sowie der Fragmentierung der Cluster besonders wichtig. Die Cluster wurden in einer gepulsten Bogenentladungsquelle erzeugt und nach Massenselektion in einem Flugzeit-Massenspektrometer mit sechs verschiedenen Oberflächen (Diamant, Siliziumdioxid, Antimon(III)oxid, Gold, Graphit und einer fluorierten organischen Monolagenoberfläche (C10-F-SAM)) unter Ultrahochvakuumbedingungen zur Wechselwirkung gebracht. Die daraus hervorgehenden ionischen Produkte wurden in einem zweiten Flugzeit-Massenspektrometer analysiert. Der Ladungstransfer zwischen Projektilion und Oberfläche zeigte deutliche Unterschiede in Abhängigkeit von der Oberfläche. Dieser Effekt wurde anhand der Gesamtfragmentionenausbeute studiert und kann gut durch die unterschiedlichen Austrittsarbeiten beschrieben werden. Die Effektivität der Oberflächen hinsichtlich des Transfers von kinetischer in innere Energie der auftreffenden Cluster ließ sich aus den Massenspektren der Fragmentionen bestimmen. Diese konnten aufgrund der bekannten Bindungsenergien der Antimon-Cluster mittels der Thermometermolekülmethode ausgewertet werden. Es wurde eine für alle Clustergrößen charakteristische Korrelation zwischen Energietransfereffektivität und Oberfläche festgestellt. Von allen untersuchten Oberflächen zeigt die F-SAM-Oberfläche den geringsten Energieübertrag. Der höchste Energieübertrag wird bei der Streuung an der Diamantoberfläche gemessen. Die Energieübertragseffektivität der anderen Oberflächen reiht sich zwischen diesen beiden Extremen ein. Diese Korrelation konnte sowohl mit makroskopischen (Härte) als auch mit mikroskopischen (Bindungsenergie, interatomare Abstände und Debye-Temperatur) Eigenschaften der zugehörigen Festkörper erklärt werden. / Surface-induced fragmentation of pure and mixed antimony clusters was investigated within the hyperthermal collision energy range. Charge transfer, energy transfer and fragmentation of the clusters are important processes in this range. Clusters were produced in a pulsed arc-discharge cluster ion source (PACIS) and mass-selected in a time-of-flight mass spectrometer. In a next step, the clusters were brought into interaction with six different surfaces (diamond, silicon dioxide, antimony(III)oxide, gold, graphite and a self-assembled organic mono-layer surface (C10-F-SAM)) under ultra-high vacuum conditions. The emerging product ions were analysed in a second time-of-flight mass spectrometer. A notable difference between the six surfaces was found with respect to the charge transfer between projectile ion and surface. This effect was analysed in considering the total fragment ion yield and can be attributed to the different work functions of these surfaces. The transfer from translational energy into vibrational modes of the impinging clusters has been determined from the mass spectra of the fragment ions as a function of the surface. The known binding energies of the antimony clusters allow the use of the thermometer molecule model to evaluate the fragment ion distribution. A correlation between the energy transfer efficiency and the type of surface was found which is valid for all cluster sizes. From all the surfaces, which have been investigated, the F-SAM surface shows the lowest and the diamond surface shows the highest energy transfer efficiency. The efficiency of the other surfaces falls in-between these two extremes. The correlation between the energy transfer efficiency of a surface and the kind of surface can be satisfactorily explained in terms of either macroscopic (hardness) or microscopic (binding energy, interatomic distances and Debye-temperature) properties of the solids.