[ES] La demanda de agua y la contaminación del agua son dos problemas ligados no solo de los últimos años sino también para el futuro. Mucho se ha hecho en el pasado para eliminar los contaminantes emergentes (CEC) de los sistemas acuáticos, utilizando diferentes tipos de técnicas; entre ellos, los mediados por luz han obtenido gran atención en los últimos años, debido a su alta eficiencia y sus bajos costos. Entre todas estas técnicas, se han desarrollado Procesos Avanzados de Oxidación y Reducción (AOPs y ARPs, respectivamente) para eliminar eficientemente las CECs. En detalle, en esta tesis se ha investigado el uso de moléculas orgánicas como fotocatalizadores en combinación con luz solar y visible; La riboflavina y la eosina Y han sido seleccionadas como fotocatalizadores por sus diferentes propiedades químicas: la primera es una molécula natural, conocida por sus propiedades oxidativas, mientras que la segunda es un colorante sintético. El objetivo principal de esta tesis doctoral fue investigar la degradación de varias clases de CEC mediante el uso de fotocatalizadores orgánicos y luz visible. En detalle, se monitorearon las tendencias de degradación de cada CEC frente al tiempo en diferentes condiciones de trabajo, con el fin de encontrar el mejor sistema de fotodegradación. Además, se investigó el mecanismo de funcionamiento mediante la determinación de los principales fotoproductos y mediante el estudio de las especies reactivas generadas, involucradas en los procesos. Se realizaron pruebas de toxicidad adicionales para tener una visión general de todos los participantes del sistema. Al final, toda la información se combinó para postular un mecanismo de degradación hipotético para todos los CEC. Más concretamente, la tesis se podría dividir en dos partes principales: en los capítulos 3 y 4 se llevó a cabo la oxidación de CECs, mientras que en los capítulos 5 y 6 se evaluaron las condiciones reductoras. En detalle, en los capítulos 3 y 4, se oxidaron tres compuestos farmacéuticos en presencia de riboflavina acetilada (RFTA) y luz visible. Específicamente, se investigaron carbamazepina, atenolol y noscapina en condiciones oxidativas. Los estudios de fotodegradación de los compuestos iniciales y de sus fotoproductos fueron importantes para comprender su oxidación natural en los sistemas acuosos naturales. Todas las vías oxidativas se consideraron en un mecanismo de degradación hipotético final. Además, en los capítulos 5 y 6, se investigó la fotodegradación de algunos ejemplos de estabilizadores UV de benzotriazol (BUVS). Los BUVS son compuestos muy recalcitrantes, que no se ven afectados en condiciones oxidativas. En consecuencia, se probaron múltiples sistemas fotocatalíticos y, finalmente, varios BUVS se degradaron en condiciones reductoras en presencia de RFTA o eosina Y (EOY) como fotocatalizadores, un donante de sacrificio como DABCO y luz visible. Al igual que en los capítulos anteriores, las mediciones fotoquímicas fueron necesarias para determinar la principal ruta de degradación y las especies químicas reactivas involucradas en el proceso. Se han realizado experimentos adicionales en presencia de otros donantes de sacrificio y agua marina para recrear un entorno natural real para estudios futuros. / [CA] La demanda d'aigua i la contaminació de l'aigua són dos problemes lligats no sols dels últims anys sinó també per al futur. Molt s'ha fet en el passat per a eliminar els contaminants emergents (CECs) dels sistemes aquàtics, utilitzant diferents tipus de tècniques; entre ells, els mediats per llum han obtingut gran atenció en els últims anys, a causa de la seua alta eficiència i els seus baixos costos. Entre totes aquestes tècniques, s'han desenvolupat Processos Avançats d'Oxidació i Reducció (AOPs i ARPs, respectivament) per a eliminar eficientment les CECs. Detalladament, en aquesta tesi s'ha investigat l'ús de molècules orgàniques com fotocatalizadores en combinació amb llum solar i visible; la riboflavina i l'eosina I han sigut seleccionades com fotocatalizadores per les seues diferents propietats químiques: la primera és una molècula natural, coneguda per les seues propietats oxidatives, mentre que la segona és un colorant sintètic. Detalladament, es van monitorar les tendències de degradació de cada CEC enfront del temps en diferents condicions de treball, amb la finalitat de trobar el millor sistema de fotodegradación. A més, es va investigar el mecanisme de funcionament mitjançant la determinació dels principals fotoproductos i mitjançant l'estudi de les espècies reactives generades, involucrades en els processos. Es van realitzar proves de toxicitat addicionals per a tindre una visió general de tots els participants del sistema. Al final, tota la informació es va combinar per a postular un mecanisme de degradació hipotètic per a tots els CEC. Més concretament, la tesi es podria dividir en dues parts principals: en els capítols 3 i 4 es va dur a terme l'oxidació de CECs, mentre que en els capítols 5 i 6 es van avaluar les condicions reductores. Detalladament, en els capítols 3 i 4, es van oxidar tres compostos farmacèutics en presència de riboflavina acetilada (RFTA) i llum visible. Específicament, es van investigar carbamazepina, atenolol i noscapina en condicions oxidatives. Els estudis de fotodegradación dels compostos inicials i dels seus fotoproductos van ser importants per a comprendre la seua oxidació natural en els sistemes aquosos naturals. Totes les vies oxidatives es van considerar en un mecanisme de degradació hipotètic final. A més, en els capítols 5 i 6, es va investigar la fotodegradación d'alguns exemples d'estabilitzadors UV de benzotriazol (BUVS). Els BUVS són compostos molt recalcitrants, que no es veuen afectats en condicions oxidatives. En conseqüència, es van provar múltiples sistemes fotocatalíticos i, finalment, diversos BUVS es van degradar en condicions reductores en presència de RFTA o eosina I (EOY) com fotocatalizadores, un donant de sacrifici com DABCO i llum visible. Igual que en els capítols anteriors, els mesuraments fotoquímics van ser necessàries per a determinar la principal ruta de degradació i les espècies químiques reactives involucrades en el procés. S'han realitzat experiments addicionals en presència d'altres donants de sacrifici i aigua marina per a recrear un entorn natural real per a estudis futurs. / [EN] Water request and water pollution are two bonded problems not only of the last years but also for the future. A lot has been done in the past in order to eliminate contaminants of emerging concerned (CECs) from the aquatic systems, using different kind of techniques; among them, those mediated by light have obtained great attention in the last years, due to their high efficiency and their low costs. Among all these techniques, Advanced Oxidation and Reduction Processes (AOPs and ARPs, respectively) have been developed in order to efficiently remove CECs. In detail, in this thesis the use of organic molecules as photocatalysts has been investigated in combination with solar and visible light; riboflavin and eosin Y have been selected as photocatalysts for their different chemical properties: the first is a natural molecule, well-known for its oxidative properties, while the second one is a synthetic dye. The main aim of this doctoral thesis was to investigate the degradation of various classes of CECs through the use of organic photocatalysts and visible light. In detail, degradation trends of each CEC was monitored vs time under different working conditions, in order to find the best photodegradation system. Moreover, the operating mechanism was investigated through the determination of the main photoproducts and through the study of the generated reactive species, involved in the processes. Additional toxicity tests were performed in order to have an overall view of all the participants of the system. At the end, all the information was combined to postulate an hypothetical degradation mechanism for all the CECs. More specifically, the thesis could be divided in two main parts: in chapters 3 and 4 oxidation of CECs was carried out, while in chapters 5 and 6 reductive conditions were evaluated. In detail, in chapters 3 and 4, three pharmaceutical compounds were oxidized in the presence of acetylated riboflavin (RFTA) and visible light. Specifically, carbamazepine, atenolol and noscapine were investigated under oxidative conditions. Photodegradation studies of the initial compounds and of their photoproducts were important in order to understand their natural oxidation in the natural aqueous systems. All the oxidative pathways were considered in a final hypothetical degradation mechanism. Moreover, in chapters 5 and 6, the photodegradation of a few examples of the benzotriazole UV-stabilizers (BUVSs) was investigated. BUVSs are very recalcitrant compounds, not affected under oxidative conditions. Consequentially, multiple photocatalytic systems were tested and finally, various BUVSs were degraded under reductive conditions in the presence of RFTA or eosin Y (EOY) as photocatalysts, a sacrificial donor as DABCO and visible light. As in the previous chapters, photochemical measurements were necessary to determine the main degradation pathway and the reactive chemical species involved in the process. Additional experiments in the presence of other sacrificial donors and marine water have been performed in order to recreate a real natural environment for future studies. / Pavanello, A. (2022). Novel Mechanistic Insights on the Photoredox Degradation of CECs Using Organic Photocatalysts [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191002

In this work, experimental and theoretical approaches are applied to the study of chemical reaction dynamics. In Chapter 2, two applications of transition state theory are presented: (1) Application of microcanonical transition state theory to determine the rate constant of dissociation of C2F3I after π∗ ← π excitation. It was found that this reaction has a very fast rate constant and thus is a promising system for testing the statistical assumption of molecular reaction dynamics. (2) A general rate constant expression for the reaction of atoms and molecules at surfaces was derived within the statistical framework of flexible transition state theory. In Chapter 4, a computationally efficient TDDFT approach was found to produce useful potential energy surface landscapes for application to non-adiabatic predissociative dynamics of the molecule CS2 after excitation from the ground state to the singlet C-state. In Chapter 5, ultrafast experimental results of excitation of CS2 to the predissociative neutral singlet C-state is presented. The bandwidth of the excitation laser was carefully tuned to span a two-component scattering resonance with each component differently evolving electronically with respect to excited state character during the quasi-bound oscillation. Scalar time-resolved photoelectron spectra (TRPES) and vector time-resolved photoelectron angular distribution (TRPAD) observables were recorded during the predissociation. The TRPES yield of photoelectrons was found to oscillate with a quantum beat pattern for the photoelectrons corresponding to ionization to the vibrationless cation ground state; this beat pattern was obscured for photoelectron energies corresponding to ionization from the vibrationally excited CS2 cation. The TRPAD data was recorded for two general molecular ensemble cases: with and without a pre-excitation alignment laser pulse. It was found that in the case of ensemble alignment (Chapter 6), the “molecular frame” TRPAD (i.e. TRMFPAD) was able to image the purely valence electronic dynamics of the evolving CS2 C-state. The unaligned ensemble TRPAD observable suffers from excessive orientational averaging and was unable to observe the quantum beat. Engineering efforts were also undertaken to eliminate scattered light background signal (Chapter 7, Appendix A) and improve laser stability as a function of ambient pressure (Appendix B) for TRMFPAD experiments. / Thesis (Ph.D, Chemistry) -- Queen's University, 2012-09-11 22:18:20.89

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Substitutional dopants in III-V semi-conductors, such as Si atoms in GaAs, are of great interest for the applications in transistors, Schottky diodes, and doping super-lattices which have been widely employed to control the electrical properties of semi-conductors. Although Si doped GaAs systems have been intensively investigated theoretically and experimentally in the last several decades, some properties are still debated. In order to give a further explanation of Si doped GaAs systems, we systematically studied DX center in bulk GaAs and in GaAs(110), as well as the relative stabilities of different charged systems for Si atom replacing Ga atom at the substitutional site near GaAs(110) surface from first principles ground state method. We show that DX centre is a metastable state in bulk GaAs and completely unstable in the top few layers of GaAs(110). When Si atom replaces Ga atom at the surface, Charge states have an important influence on the stability of the system, and the additional charge is mainly concentrated on the Si atom for charged system. In addition, we studied the STM images of clean GaAs(110) and charged Si:GaAs(110) by employing Tersoff-Hamann approximation. The calculated STM images are in good agreement with experimental results. We show that at the positive bias voltage the positively charged Si atom presents a bright feature while the negatively charged Si atom shows a dark feature. In a semi-conductor, all bands are either completely full or completely empty. It is well known that DFT underestimates the band gaps of semi-conductors, a simple rigid shift can be used to correct the band energies of semi-conductors. Unlike semi-conductor, the fermi energies of metals lie in some bands. Furthermore, it turned out that some noble metals such as Cu and Ag depend on the considered band and k point , therefore, the so-called scissors operator can not be used for the metallic systems. The most successful approach within theoretical method for these metals is the many body perturbation theory. On the other hand, an interesting study for metals is quasi-particle excitations, which play an important role in a rich variety of physical and chemical phenomena such as energy transfer in photochemical reaction, desorption and oxidation of molecules at surfaces, spin transport within bulk metals, across interfaces, and at surfaces. One of the crucial properties of quasi-particle excitation is their lifetimes which determine the duration of these excitations. We carried out the calculations of quasi-particle band-structures and lifetimes for noble metals Cu and Ag within the GW approximation. For Cu, both the calculated positions of the d bands and the width of the d bands is within 0.1 eV compared to the experimental results. For Ag, partial core correction should be included in the pseudo-potential to get reliable positions of the d bands. The calculated lifetime agree with the experiment in the energy region away from the Fermi level, but deviates from the experimental results near the Fermi level where short range interactions which GW approach fails to describe play an important role. For a better description of the lifetime near the Fermi level, higher terms beyond the GW approximation in the many body perturbation theory need to be considered. In addition, the image potential state lifetimes in Cu(100) have been calculated using GW approximation based on the localized Gaussian basis set, and the calculated n=1, 2 imagepotential state lifetimes are in good agreement with experimental results.

L’étude de la dissociation de molécules poly-atomiques en surface est d’une importance à la fois fondamentale et industrielle. La compréhension du mécanisme et la dynamique réactionnelle sous-jacents représente un défi. Comme un système modèle, la dissociation de méthane sur la surface de nickel a fait l’objet de nombreuses études pour élucider les chemins de réaction et le transfert d’énergie parmi les différents degrés de liberté durant la réaction. La mode-spécifique ou liaison-spécifique réactivité pour la dissociation de CH4 sur Ni(111) et Ni(100) ont été mise en évidence récemment par des expériences de pointe du jet moléculaire. Jusqu’à présent, les études théoriques de la dynamique réactionnelle ont été effectuées avec un modèle simplifié dans lequel CH4 est décrit comme une molécule pseudo-diatomique. Le concept d’un groupe méthyle spectateur introduit dans un tel modèle impose des contraintes drastiques. Par exemple, l’indiscernabilité des quatre liaisons C-H de méthane est violée par le fait que la liaison C-H capable de se dissocier se singularise par rapport aux trois autres liaisons inertes. En réalité, n’importe quelle des quatre liaisons est susceptible de se dissocier. Par ailleurs, l’unique mode vibrationnel du modèle pseudo-diatomique ne ressemble à aucun des quatre modes vibrationnels principaux du méthane, qui décrivent tous des mouvements collectifs de plusieurs atomes. Lorsque tous les degrés de liberté sont pris en compte, la dimensionnalité de la surface de l’énergie potentielle pour CH4/Ni(111) est très élevée (15 degrés de liberté pour CH4 et certains degrés de liberté du substrat). Construire une surface de l’énergie potentielle fiable à une telle grande dimension est, en soi, un grand défi. A notre connaissance, ce défi n’a jamais été tenté auparavant pour quelconque réaction d’une molécule poly-atomique sur une surface métallique. En utilisant un champ de force réactif, nous avons développé, dans le présent travail, une surface de l’énergie potentielle qui prend en compte tous les 15 degrés de liberté de CH4 ainsi que ceux des 3 premières couches de NI(111). Des simulations de dynamique moléculaire ont été effectuées pour étudier la dynamique réaction de CH4 sur Ni(111) aussi bien dans son état fondamental vibrationnel que dans un état excité. Ces simulations ont permis de révéler des comportements dynamiques inattendus et très intéressants. / In the present work, we undertook a challenging task, i.e., construction a full-dimension potential energy surface (PES) for a benchmark poly-atomic molecular surface reaction, CH4/Ni(111), by using a reactive force field. Careful appraisal of the PES was made in order to establish the validity of the PES. The differences between the results for the transition state (dissociation barriers and structures) given by our PES and those by DFT calculations do not exceed 15%. The molecular dynamics simulation results obtained by using our PES are compared to experimental results for CH4 dissociation probability on Ni(111). For the vibrationally excited state, v3 (v=1, J=0), the agreement between our simulation results and the experimental ones is excellent. For the ground state, the sticking coefficient is somehow over-estimated because of the under-estimation of the dissociation barrier by about 150 meV with our reactive force field. Nevertheless, the overall agreement between simulation and experiment is pretty good. Within the help of the full-dimensional PES, we have extensively studied some important aspects of reaction dynamics, e.g., the effects of surface impact position, surface temperature, vibrationally excited state, rotationally excited states etc. For CH4 in ground state (v=0, J=0), the investigation of the effect of CH4 impact position shows that the top site is the most reactive one. The surface temperature strongly affects the reactivity of methane, especially in the region of the low incident energy near to the dissociation threshold, while in the high incident energy region, the effect is less important. For CH4 v3 (v=1, J=0), an important coupling between rotation and vibration is found. The rotation of CH4 can enhance its reactivity in the following way. In its ground state (v=0, J=0), CH4 does not rotate during its flight to the surface. In this case, only one of the two lowest C-H bonds pointing initially toward the surface can be cleaved while the two other bonds never break. In v3 (v=1, J=0) vibrational state, due to the rotation induced by vibration-rotation coupling, any of the four H atoms can be dissociated even if it forms a C-H bond which has an unfavorable initial orientation (i.e., pointing away from the substrate). The rotation of CH4 induced by vibration-rotation coupling near the substrate allows for bringing an unfavorable initial orientation of C-H bond to the right one required by a transition state (TS) during the adsorbate’s approaching to the substrate. As the enhanced reactivity of vibrationally excited molecules is concerned, the intuitively limpid and overwhelmingly accepted explanation is that the vibration-induced bond stretching helps bond breaking. Our simulation results show clearly that the vibration-induced CH4 rotation contributes an important part to the enhanced reactivity of a v3 (v=1, J=0) vibrationally excited CH4. A series of simulations to determine the sticking curves for CH4 in the vibrational ground state (ν=0) but excited to higher rotational levels (J=0-12) have also been performed. Due to its small level spacing, the lowest rotational excited states (J=1-3) of CH4 do not affect its reactivity on Ni(111) as observed experimentally. We found that rotation enhances significantly CH4 reactivity on Ni(111) with a deposited rotational energy amounting only to 12% of the dissociation barrier. Moreover, in a hypothetic simulation, we found also very striking evidences that rotation can even promote better dissociation of CH4 on Ni(111) than vibration. In a vibrationally excited CH4, its C-H bonds undergo alternate stretching and compressing and the latter hinders dissociation. In this case, the reactivity is inevitably modulated by vibration phase. However, the centrifugal force due to rotation tends always to stretch the C-H bonds for CH4 in rotationally excited states. / 多原子气相分子的分解，不仅在物理，化学及相关学科有着基本的重要性，而且可以促进工业进程，如工业制氢气。对其涉及的反应，即化学键的断裂与形成，在理解其反应机制和动力学上更是一项挑战。作为多原子气相-固相化学反应中最为典型的反应，甲烷分子在金属镍表面的分解，已经被广泛地研究从而理解其在动力学过程中的能量转化和反应路径。最近，选态分子束实验报道了有关甲烷在镍表面分解反应的重要特征，即模式选择性和化学键选择性。从理论角度来看，以前大多数理论研究都是基于一个简化模型，即将甲烷分子看成是一个赝双原子分子(CH4=RH,其中R=CH3)。在该简化模型中，将甲基团当做一个“spectator”会导致严重的限制性，如四个碳氢键的不可分辨性就被破坏。因为在简化模型中，只有一个可分解的碳氢键而其他三个碳氢键则被保护起来；而在实际的分解反应过程中，甲烷分子的任何一个碳氢化学键应该都有概率被分解掉。此外，在该赝双原子分子模型中，单键伸长振动模式不能类比于甲烷的四个基本振动模式，因为其每种基本振动模式都涉及多个原子的复合运动。如果不将甲烷处理成赝双原子分子，那么该体系（CH4/Ni(111)）的势能面的维度会很高，即甲烷的15 个自由度加上部分基地原子的自由度。欲建立一个如此高维度而且又可靠的势能面，本身就是一个值得挑战的研究任务。据我们所知，目前对多原子分子在金属表面反应的高维度势能面的报道几乎没有。在本论文中，我们运用键序反应力场（REBO），为体系CH4/Ni(111)，首次建立起一个全维度的势能面。该势能面的维度包含甲烷的15 个自由度和3 层基地原子的自由度。在经典分子动力学（和准经典分子动力学）模拟下，我们研究了甲烷处于基态和激发态时在金属表面的分解活性，并发现了一些非常有趣的结果。本论文包含以下六章：第一章：简单介绍了甲烷在过渡金属表面分解的最新进展。在选态分子束试验报道中，我们介绍了一些有关该反应的重要特征，如模式选择性，化学键选择性，表面温度效应，空间效应，旋转激发效应等。在理论工作方面，主要介绍了两个理论研究小组近期在简化模型下的一些量子动力学结果。第二章：对本文所运用的理论方法和近似做了基本的介绍。这些方法主要归纳于两类：i)电子结构计算；ii) 分子动力学模拟。我们重点介绍了这些方法和近似的特征。第三章：我们运用二阶矩近似力场(SMA)和键序反应力场(REBO)模拟了氢分子在金属钯表面的分解反应, 从而验证反应力场在模拟表面化学反应的适用性。该章讨论了在参数化反应力场时的一些影响因素，如有效数据库大小，不同排斥势以及长程作用项等，为对复杂体系的研究提供了有效的帮助。第四章：基于键序反应力场(REBO)，我们首次为CH4/Ni(111) 体系建立起一个全维度势能面(PES)。同时我们对该势能面(REBO(PES))做了全面评估，如比较势能面(REBO(PES))与DFT计算得到的过渡状态结构和与之对应的分解势垒，比较两者对于不同形式相互作用给出的势能变化等。此外，我们还直接模拟了甲烷在基态时的活性，其模拟结果与实验有着很好的符合度，从而进一步地说明了该势能面(REBO(PES))的可靠性。第五章：在全维度势能面下，我们深入地研究了甲烷处于不同状态时在镍表面分解的反应活性，即基态(v=0,J=0)，反对称振动态v3 (v=1,J=0)和旋转激发态(v=0,J=1-12)。对于基态的甲烷，我们定性并定量地分析了表面碰撞位置，表面温度对其分解概率的影响。对于反对称振动态的甲烷，我们观察到振动激发态的甲烷分子反应活性比基态甲烷的反应活性要大大地增强。究其根源在于，平动能量不易转换至旋转自由度，而振动能量则非常容易转入到旋转自由度。我们利用三个定量参数详细地阐述了这种振动耦合转动的重要性。此外，对于甲烷处于旋转激发态时，我们发现其激发状态非常有利于甲烷的分解，尽管其旋转能量只有分解势垒的12%。更为惊奇的是，对于甲烷分子而言，其旋转激发态比振动激发态更有利于其分解。其相应的物理解释是，对于振动激发的甲烷，它的碳氢键处于伸长与收缩的交替中，而后者却阻止其分解。对于旋转激发中的甲烷，其离心力一直促使碳氢键的伸长。第六章：总结和展望。我们总结了本文的主要结论以及给出一些将来需要进行的工作，如同位素效应等。

In dieser Dissertation werden ab initio Theorien zur Beschreibung der Zustände von perfekten halbleitenden und nichtleitenden Kristallen, unter Berücksichtigung elektronischer Korrelationen, abgeleitet und angewandt. Als Ausgangsbasis dient hierzu die Hartree-Fock Approximation in Verbindung mit Wannier-Orbitalen. Darauf aufbauend studiere ich zunächst in Teil I der Abhandlung den Grundzustand der wasserstoffbrückengebundenen Fluorwasserstoff und Chlorwasserstoff zick-zack Ketten und analysiere die langreichweitigen Korrelationsbeiträge. Dabei mache ich die Basissatzextrapolationstechniken, die für kleine Moleküle entwickelt wurden, zur Berechnung von hochgenauen Bindungsenergien von Kristallen nutzbar. In Teil II der Arbeit leite ich zunächst eine quantenfeldtheoretische ab initio Beschreibung von Elektroneneinfangzuständen und Lochzuständen in Kristallen her. Grundlage hierbei ist das etablierte algebraische diagrammatische Konstruktionsschema (ADC) zur Approximation der Selbstenergie für die Bestimmung der Vielteilchen-Green's-Funktion mittels der Dyson-Gleichung. Die volle Translationssymmetrie des Problems wird hierbei beachtet und die Lokalität elektronischer Korrelationen ausgenutzt. Das resultierende Schema wird Kristallorbital-ADC (CO-ADC) genannt. Ich berechne damit die Quasiteilchenbandstruktur einer Fluorwasserstoffkette und eines Lithiumfluoridkristalls. In beiden Fällen erhalte ich eine sehr gute Übereinstimmung zwischen meinen Resultaten und den Ergebnissen aus anderen Methoden. / In this dissertation, theories for the ab initio description of the states of perfect semiconducting and insulating crystals are derived and applied. Electron correlations are treated thoroughly based on the Hartree-Fock approximation formulated in terms of Wannier orbitals. In part I of the treatise, I study the ground state of hydrogen-bonded hydrogen fluoride and hydrogen chloride zig-zag chains. I analyse the long-range contributions of electron correlations. Thereby, I employ basis set extrapolation techniques, which have originally been developed for small molecules, to also obtain highly accurate binding energies of crystals. In part II of the thesis, I devise an ab initio description of the electron attachment and electron removal states of crystals using methods of quantum field theory. I harness the well-established algebraic diagrammatic construction scheme (ADC) to approximate the self-energy, used in conjunction with the Dyson equation, to determine the many-particle Green's function for crystals. Thereby, the translational symmetry of the problem and the locality of electron correlations are fully exploited. The resulting scheme is termed crystal orbital ADC (CO-ADC). It is applied to obtain the quasiparticle band structure of a hydrogen fluoride chain and a lithium fluoride crystal. In both cases, a very good agreement of my results to those determined with other methods is observed.

In dieser Dissertation werden ab initio Theorien zur Beschreibung der Zustände von perfekten halbleitenden und nichtleitenden Kristallen, unter Berücksichtigung elektronischer Korrelationen, abgeleitet und angewandt. Als Ausgangsbasis dient hierzu die Hartree-Fock Approximation in Verbindung mit Wannier-Orbitalen. Darauf aufbauend studiere ich zunächst in Teil I der Abhandlung den Grundzustand der wasserstoffbrückengebundenen Fluorwasserstoff und Chlorwasserstoff zick-zack Ketten und analysiere die langreichweitigen Korrelationsbeiträge. Dabei mache ich die Basissatzextrapolationstechniken, die für kleine Moleküle entwickelt wurden, zur Berechnung von hochgenauen Bindungsenergien von Kristallen nutzbar. In Teil II der Arbeit leite ich zunächst eine quantenfeldtheoretische ab initio Beschreibung von Elektroneneinfangzuständen und Lochzuständen in Kristallen her. Grundlage hierbei ist das etablierte algebraische diagrammatische Konstruktionsschema (ADC) zur Approximation der Selbstenergie für die Bestimmung der Vielteilchen-Green's-Funktion mittels der Dyson-Gleichung. Die volle Translationssymmetrie des Problems wird hierbei beachtet und die Lokalität elektronischer Korrelationen ausgenutzt. Das resultierende Schema wird Kristallorbital-ADC (CO-ADC) genannt. Ich berechne damit die Quasiteilchenbandstruktur einer Fluorwasserstoffkette und eines Lithiumfluoridkristalls. In beiden Fällen erhalte ich eine sehr gute Übereinstimmung zwischen meinen Resultaten und den Ergebnissen aus anderen Methoden. / In this dissertation, theories for the ab initio description of the states of perfect semiconducting and insulating crystals are derived and applied. Electron correlations are treated thoroughly based on the Hartree-Fock approximation formulated in terms of Wannier orbitals. In part I of the treatise, I study the ground state of hydrogen-bonded hydrogen fluoride and hydrogen chloride zig-zag chains. I analyse the long-range contributions of electron correlations. Thereby, I employ basis set extrapolation techniques, which have originally been developed for small molecules, to also obtain highly accurate binding energies of crystals. In part II of the thesis, I devise an ab initio description of the electron attachment and electron removal states of crystals using methods of quantum field theory. I harness the well-established algebraic diagrammatic construction scheme (ADC) to approximate the self-energy, used in conjunction with the Dyson equation, to determine the many-particle Green's function for crystals. Thereby, the translational symmetry of the problem and the locality of electron correlations are fully exploited. The resulting scheme is termed crystal orbital ADC (CO-ADC). It is applied to obtain the quasiparticle band structure of a hydrogen fluoride chain and a lithium fluoride crystal. In both cases, a very good agreement of my results to those determined with other methods is observed.

In dieser Arbeit setzen wir ab-initio-Methoden zur Untersuchung einiger Oberflächensysteme und eines Bulksystems ein. Im Wesentlichen greifen wir hierbei auf die Dichtefunktionaltheorie (DFT) und die GW-Approximation (GWA) im Rahmen der Vielteilchenstörungstheorie zurück. Wir nutzen diese Methoden um die Adsorption von TMA auf der Rutil TiO2-Oberfläche zu untersuchen, optische Spektren von TiO2 zu berechnen und um die Adsorption von [7]-HCA auf der Calcit(10-14)-Oberfläche zu verstehen. Weiterhin beschäftigen wir uns intensiv mit PTCDA auf Ag(111), welches mit einer chemisch kontaktierten STM-Spitze manipuliert wird.