Tesis sobre el tema "Cluster approximation"
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Zhang, Kai. "Kernel-based clustering and low rank approximation /". View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CSED%202008%20ZHANG.
Texto completoBenedikt, Udo. "Low-Rank Tensor Approximation in post Hartree-Fock Methods". Doctoral thesis, Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-133194.
Texto completoDie vorliegende Arbeit beschäftigt sich mit der Anwendung neuartiger Tensorzerlegungs- und Tensorrepesentationstechniken in hochgenauen post Hartree-Fock Methoden um das hohe Skalierungsverhalten dieser Verfahren mit steigender Systemgröße zu verringern und somit den "Fluch der Dimensionen" zu brechen. Nach einer vergleichenden Betrachtung verschiedener Representationsformate wird auf die Anwendung des "canonical polyadic" Formates (CP) detailliert eingegangen. Dabei stehen zunächst die Umwandlung eines normalen, indexbasierten Tensors in das CP Format (Tensorzerlegung) und eine Methode der Niedrigrang Approximation (Rangreduktion) für Zweielektronenintegrale in der AO Basis im Vordergrund. Die entscheidende Größe für die Anwendbarkeit ist dabei das Skalierungsverhalten das Ranges mit steigender System- und Basissatzgröße, da der Speicheraufwand und die Berechnungskosten für Tensormanipulationen im CP Format zwar nur noch linear von der Anzahl der Dimensionen des Tensors abhängen, allerdings auch mit der Expansionslänge (Rang) skalieren. Im Anschluss wird die AO-MO Transformation und der MP2 Algorithmus mit zerlegten Tensoren im CP Format diskutiert und erneut das Skalierungsverhalten mit steigender System- und Basissatzgröße untersucht. Abschließend wird ein Coupled-Cluster Algorithmus vorgestellt, welcher ausschließlich mit Tensoren in einer Niedrigrang CP Darstellung arbeitet. Dabei wird vor allem auf die sukzessive Tensorkontraktion während der iterativen Bestimmung der Amplituden eingegangen und die Fehlerfortpanzung durch Anwendung des Rangreduktions-Algorithmus analysiert. Abschließend wird die Komplexität des gesamten Verfahrens bewertet und Verbesserungsmöglichkeiten der Reduktionsprozedur aufgezeigt
Scherrer, Alexander. "Adaptive approximation of nonlinear minimization problems : the adaptive clustering method in inverse radiation therapy planning /". Aachen : Shaker, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015733837&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Texto completoFilor, Stephan [Verfasser], Stefan [Akademischer Betreuer] [Gutachter] Kehrein y Andreas [Gutachter] Honecker. "A Variational Cluster Approximation for the Heisenberg Model / Stephan Filor ; Gutachter: Stefan Kehrein, Andreas Honecker ; Betreuer: Stefan Kehrein". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1129956415/34.
Texto completoFilor, Stephan Verfasser], Stefan [Akademischer Betreuer] [Gutachter] [Kehrein y Andreas [Gutachter] Honecker. "A Variational Cluster Approximation for the Heisenberg Model / Stephan Filor ; Gutachter: Stefan Kehrein, Andreas Honecker ; Betreuer: Stefan Kehrein". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1129956415/34.
Texto completoSen, Asok Kumar. "Part I, traveling cluster approximation for uncorrelated amorphous systems ; Part II, influence of long-range forces on the wetting transition /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487260859496667.
Texto completoHeinen, Milton Roberto. "A connectionist approach for incremental function approximation and on-line tasks". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/29015.
Texto completoThis work proposes IGMN (standing for Incremental Gaussian Mixture Network), a new connectionist approach for incremental function approximation and real time tasks. It is inspired on recent theories about the brain, specially the Memory-Prediction Framework and the Constructivist Artificial Intelligence, which endows it with some unique features that are not present in most ANN models such as MLP, RBF and GRNN. Moreover, IGMN is based on strong statistical principles (Gaussian mixture models) and asymptotically converges to the optimal regression surface as more training data arrive. The main advantages of IGMN over other ANN models are: (i) IGMN learns incrementally using a single scan over the training data (each training pattern can be immediately used and discarded); (ii) it can produce reasonable estimates based on few training data; (iii) the learning process can proceed perpetually as new training data arrive (there is no separate phases for leaning and recalling); (iv) IGMN can handle the stability-plasticity dilemma and does not suffer from catastrophic interference; (v) the neural network topology is defined automatically and incrementally (new units added whenever is necessary); (vi) IGMN is not sensible to initialization conditions (in fact there is no random initialization/ decision in IGMN); (vii) the same neural network can be used to solve both forward and inverse problems (the information flow is bidirectional) even in regions where the target data are multi-valued; and (viii) IGMN can provide the confidence levels of its estimates. Another relevant contribution of this thesis is the use of IGMN in some important state-of-the-art machine learning and robotic tasks such as model identification, incremental concept formation, reinforcement learning, robotic mapping and time series prediction. In fact, the efficiency of IGMN and its representational power expand the set of potential tasks in which the neural networks can be applied, thus opening new research directions in which important contributions can be made. Through several experiments using the proposed model it is demonstrated that IGMN is also robust to overfitting, does not require fine-tunning of its configuration parameters and has a very good computational performance, thus allowing its use in real time control applications. Therefore, IGMN is a very useful machine learning tool for incremental function approximation and on-line prediction.
Choudhury, Salimur Rashid y University of Lethbridge Faculty of Arts and Science. "Approximation algorithms for a graph-cut problem with applications to a clustering problem in bioinformatics". Thesis, Lethbridge, Alta. : University of Lethbridge, Deptartment of Mathematics and Computer Science, 2008, 2008. http://hdl.handle.net/10133/774.
Texto completoxiii, 71 leaves : ill. ; 29 cm.
Nachaoui, Mourad. "Étude théorique et approximation numérique d'un problème inverse de transfert de la chaleur". Phd thesis, Université de Nantes, 2011. http://tel.archives-ouvertes.fr/tel-00678032.
Texto completoMadjet, Mohamed El-Amine. "Etude théorique des propriétés électroniques et dynamiques des agrégats métalliques simples dans le modèle du jellium". Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10094.
Texto completoBOTTO, DAVIDE. "Dynamical transitions in driven diffusive models". Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2790160.
Texto completoEkdahl, Magnus. "Approximations of Bayes Classifiers for Statistical Learning of Clusters". Licentiate thesis, Linköping : Linköpings universitet, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5856.
Texto completoDe, Silva Shalutha. "Force controlled hexapod walking". Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/78978/1/Karunakalage_De%20Silva_Thesis.pdf.
Texto completoVimont, Guillaume. "Approximation dynamique de clusters dans un graphe social : méthodes et applications". Thesis, Paris 2, 2019. http://www.theses.fr/2019PA020007.
Texto completoWe study how to detect clusters in a graph defined by a stream of edges, without storing the entire graph. We show how to detect large clusters in the order of √n in graphs that have m = O(n log(n)) edges, while storing √n.log(n) edges. Social graphs satisfy this condition m. We extend our approach to dynamic graphs defined by the most recent stream of edges and multiple streams. We propose simple and robust methods based on the approximation to detect these clusters.We define the content correlation of two streams ρ(t) is the Jaccard similarity of their clusters in the windows before time t. We propose a simple and efficient method to approach this online correlation and show that for dynamic random graphs that follow a power law, we can guarantee a good approximation.As an applications we follow Twitter streams and compute their content correlations online. We then propose a search by correlation where answers to sets of keywords are entirely based on the small correlations of the streams. Answers are ordered by the correlations, and explanations can be traced with the stored clusters
Gutlé, Claudine. "Espaces orbitalaires et théorie de la fonctionnelle de la densité : éléments pour le développement d' une approche de la chimie quantique basée sur le théorème de Hohenberg et Kohn ainsi que sur l' équation de Schrödinger, et qui conduit à des résultats exacts en suivant une systématique gouvernée par l' espace orbitalaire". Paris 7, 2003. http://www.theses.fr/2003PA077160.
Texto completoGibson, Matthew Richard. "Clusters and covers: geometric set cover algorithms". Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/502.
Texto completoKubát, Milan. "Borcení časové osy v oblasti biosignálů". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220845.
Texto completoJacobson, Leif David. "Approximating Many-Body Induction to Efficiently Describe Molecular Liquids and Clusters With Improved Accuracy". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1312480919.
Texto completoChristlmaier, Evelin Martine. "CC2 response method using local correlation and density fitting approximations for the calculation of the electronic g-tensor of extended open-shell molecules". Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22835.
Texto completoThis work presents an unrestricted coupled-cluster CC2 response method using local correlation and density fitting approximations for the calculation of first and second order properties with particular focus on the electronic g-tensor. The fundamental concepts related to coupled-cluster theory, density fitting, local correlation, general coupled-cluster properties and the electronic g-tensor are discussed. The calculated g-tensors are benchmarked against those obtained from coupled-cluster singles and doubles, density functional theory and experiment. Efficiency and accuracy of the approximations is investigated. A detailed appendix covers the fundamentals of diagrammatic coupled-cluster and its application to the derivation of the working equations. The method presented in this thesis enables the quantitative prediction of the electronic g-tensor of extended systems with a method other than density functional theory. It represents an important step towards the development of low-scaling higher order coupled-cluster methods for this type of problem.
Ndoye, Chérif A. A. "Electronic spectroscopy of small organic and organometallic molecules : electronic correlation, vibronic and spin-orbit couplings". Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/public/theses_doctorat/2008/NDOYE_Cherif_AA_2008.pdf.
Texto completoTheory is sometime necessary to predict molecular spectroscopic properties and interpret experimental spectra. A first step study can be limited to the electronic spectroscopy in Born-Oppenheimer approximation which consists in considering nuclei fixed and electronic states independent from each other. The scope of this thesis is to first study the electronic structure of small organic and orgnometallic molecules in the Born-Oppenheimer approximation and ultimatly go beyond by taking into account effects such as vibronic or spin-orbit couplings between electronic states. The first chapter is dedicated to the ab initio methods used to obtain the results presented in the following chapters. Electronic structure methods in the Born-Oppenheimer approximation are first presented followed by the methods that treat vibronic and spin-orbit couplings. The second chapter is a study of the electronic structure and potential energy curves of MCH+2 (M=Fe, Co, Ni) transition metal carbenes. Chapter three reports simulated vibronic spectra of fluoroethylenes, they are compared to experimental spectra to indentify the origin of the different spectroscopic contributions. A last chapter deals with the spin-orbit effects in water and its heavy homologous (H2X with X=O, Te, Po)
Plagne, Laurent. "Equation de Vlasov appliquée à la dynamique électronique des agrégats de sodium lors de collisions avec des ions". Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10272.
Texto completoMiti, Filippo. "Mathematical models for cellular aggregation: the chemotactic instability and clustering formation". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12020/.
Texto completoPham, The Anh. "Détection robuste de jonctions et points d'intérêt dans les images et indexation rapide de caractéristiques dans un espace de grande dimension". Thesis, Tours, 2013. http://www.theses.fr/2013TOUR4023/document.
Texto completoLocal features are of central importance to deal with many different problems in image analysis and understanding including image registration, object detection and recognition, image retrieval, etc. Over the years, many local detectors have been presented to detect such features. Such a local detector usually works well for some particular applications but not all. Taking an application of image retrieval in large database as an example, an efficient method for detecting binary features should be preferred to other real-valued feature detection methods. The reason is easily seen: it is expected to have a reasonable precision of retrieval results but the time response must be as fast as possible. Generally, local features are used in combination with an indexing scheme. This is highly needed for the case where the dataset is composed of billions of data points, each of which is in a high-dimensional feature vector space
Filor, Stephan. "A Variational Cluster Approximation for the Heisenberg Model". Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0023-3E15-1.
Texto completoMartin, Lee C. "The Kondo Lattice Model: a Dynamical Cluster Approximation Approach". Doctoral thesis, 2010. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-49446.
Texto completoWir setzen eine Implementierung der dynamischen Cluster Näherung (DCA) mit gebrochener Symmetrie ein um das zweidimensionale lochdotierte Kondo Gitter Model (KLM) mit dem Hüpfmatrixelement $t$ und der Kopplung $J$ zu untersuchen. Die DCA beruht auf einer Näherung der Selbstenergie. Kurzreichweitige Korrelationen auf einem kleinen Cluster, der selbstkonsistent in ein Bad der übrigen Systemelektronen eingebettet ist, werden exakt behandelt, während langreichweitige Korrelationen auf Mean-Field Basis berücksichtigt werden. Dabei wird jedoch die Dynamik des Systems voll beibehalten. Auf Grund starker dynamischer Korrelationen zeigt sich das KLM als besonders geeignet für Untersuchungen im Rahmen der DCA. Präzise Berechnungen der Einteilchen Spektralfunktion geben gute Übereinstimmung mit exakten Gitter-QMC Resultaten am Teilchen-Loch symmetrischen Punkt. Unsere DCA Version, kombiniert mit einem QMC Cluster Solver, erlaubt es, Simulationen fern vom Teilchen-Loch symmetrischen Punkt durchzuführen und hat es uns ermöglicht das magnetische Phasendiagram des Models als Funktion der Dotierung und der Kopplung $J/t$ abzutasten. Bei halber Füllung zeigen unsere Resultate, dass das lineare Verhalten der Quasiteilchenlücke bei kleinem $J/t$ direkt aus der vorliegenden Teilchen-Loch Symmetrie, die ihrerseits zu Nesting führt, hervorgeht. Brechung dieser Symmetrie durch das Einführen eines diagonalen Hüpfmatrixelements, hat eine an die Kondo Skala gekoppelte, stark reduzierte Quasiteilchenlücke zur Folge. Im dotiertem System setzt sich die bei Halbfüllung beobachtete magnetische Phase fort bis sie letztendlich der paramagnetischen Phase weicht. Wir verfolgen die Entwicklung der Topologie der Fermifläche beim Durchstoßen dieses magnetischen Übergangs vom Ordnungs- zum Unordnungregime. Das Phasendiagram unterteilt sich in drei verschiedenen Regionen: Den Paramagnetischen Bereich mit {\it großer} Fermifläche, in dem die magnetische Momente zum Luttinger Volumen beitragen, den schwachen Antiferromagneten, mit großer Fermiflächetopologie, und den starken Antiferromagneten mit {\it kleiner} Fermifläche, bei dem die magnetischen Momente nicht am Luttinger Volumen beteiligt sind. Wir beziehen uns zur weiteren Interpretation unserer DCA Resultate auf einen Mean-Field Hamiltonian mit Ordnungsparametern sowohl für die Magnetisierung als auch für die Kondo-Abschirmung. Erste Resultate bei fester Kopplung und Dotierung, jedoch bei unterschiedlichen Temperaturen, zwecks der Ermittlung der verschiedene Energieskalen des Systems, werden dargestellt. Wir suchen Signale der Kondo Temperatur $T_{K}$ bei der die Kondo-Abschirmung der magnetische Momente einsetzt, der Neel Temperatur $T_{N}$ der antiferromagnetischem Ordnung, das eventuelle Auftreten einer durch $T^{*}$ gekennzeichnete Änderung der Fermiflächen Topologie, und letztendlich die Ausbildung eines kohärenten schwerfermionischen Zustandes bei $T_{coh}$
Benedikt, Udo. "Low-Rank Tensor Approximation in post Hartree-Fock Methods". Doctoral thesis, 2013. https://monarch.qucosa.de/id/qucosa%3A19999.
Texto completoDie vorliegende Arbeit beschäftigt sich mit der Anwendung neuartiger Tensorzerlegungs- und Tensorrepesentationstechniken in hochgenauen post Hartree-Fock Methoden um das hohe Skalierungsverhalten dieser Verfahren mit steigender Systemgröße zu verringern und somit den "Fluch der Dimensionen" zu brechen. Nach einer vergleichenden Betrachtung verschiedener Representationsformate wird auf die Anwendung des "canonical polyadic" Formates (CP) detailliert eingegangen. Dabei stehen zunächst die Umwandlung eines normalen, indexbasierten Tensors in das CP Format (Tensorzerlegung) und eine Methode der Niedrigrang Approximation (Rangreduktion) für Zweielektronenintegrale in der AO Basis im Vordergrund. Die entscheidende Größe für die Anwendbarkeit ist dabei das Skalierungsverhalten das Ranges mit steigender System- und Basissatzgröße, da der Speicheraufwand und die Berechnungskosten für Tensormanipulationen im CP Format zwar nur noch linear von der Anzahl der Dimensionen des Tensors abhängen, allerdings auch mit der Expansionslänge (Rang) skalieren. Im Anschluss wird die AO-MO Transformation und der MP2 Algorithmus mit zerlegten Tensoren im CP Format diskutiert und erneut das Skalierungsverhalten mit steigender System- und Basissatzgröße untersucht. Abschließend wird ein Coupled-Cluster Algorithmus vorgestellt, welcher ausschließlich mit Tensoren in einer Niedrigrang CP Darstellung arbeitet. Dabei wird vor allem auf die sukzessive Tensorkontraktion während der iterativen Bestimmung der Amplituden eingegangen und die Fehlerfortpanzung durch Anwendung des Rangreduktions-Algorithmus analysiert. Abschließend wird die Komplexität des gesamten Verfahrens bewertet und Verbesserungsmöglichkeiten der Reduktionsprozedur aufgezeigt.
Martin, Lee C. [Verfasser]. "The Kondo lattice model : a dynamical cluster approximation approach / vorgelegt von Lee C. Martin". 2009. http://d-nb.info/1005117349/34.
Texto completoAoki, Yasunori. "Study of Singular Capillary Surfaces and Development of the Cluster Newton Method". Thesis, 2012. http://hdl.handle.net/10012/6908.
Texto completoCao, Weisheng. "Application of the cluster/site approximation to calculation of multicomponent alloy phase diagrams and coherent interphase energies". 2006. http://www.library.wisc.edu/databases/connect/dissertations.html.
Texto completoLenz, Benjamin. "Unconventional Phases in Two-Dimensional Hubbard and Kondo-Lattice Models by Variational Cluster Approaches". Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0023-3DFC-1.
Texto completoGuo, Yi-Heng y 郭奕亨. "An Approximation Algorithm for Broadcast Scheduling in Heterogeneous Clusters". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/36355502244581982459.
Texto completo國立中正大學
資訊工程研究所
90
Network of workstation (NOW) is a cost-effective alternative to massively parallel supercomputers. As commercially available off-the-shelf processors become cheaper and faster, it is now possible to build a PC or workstation cluster that provides high computing power within a limited budget. However, a cluster may consist of different types of processors and this heterogeneity within a cluster complicates the design of efficient collective communication protocols. This paper shows that a simple heuristic called fastest-node-first(FNF))[M.Banikazemi, V.Moorthy, and D.K. Panda]is very effective in reducing broadcast time for heterogeneous cluster systems. Despite the fact that FNF heuristic does not guarantee an optimal broadcast time for general heterogeneous network of workstation, we prove that FNF always gives near optimal broadcast time in a special case of cluster, and this finding helps us show that FNF delivers guaranteed performance for general clusters. In a previous paper we showed a similar bound on the competitive ratio in a send-only communication model. This paper extends the result to a more realistic sender-receiver model. We show that FNF gives a total broadcast of $2T + \beta$, where $T$ is the optimum time and $\beta$ is a constant. This improves over the previous bound on $2 \alpha T + \beta$ [Libeskind-Hadas and J.Hartline], where $\alpha$ is a theoretically unbounded ratio of the processor performance in the cluster.
Hsu, KoChung y 許克仲. "The approximation algorithm for broadcast scheduling in synchronous heterogeneous clusters". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/20516305079060859107.
Texto completo國立臺灣大學
資訊工程學研究所
91
Network of workstation (NOW) is a cost-effective alternative to massively parallel supercomputers. As commercially available off-the-shelf processors become cheaper and faster, it is now possible to build a PC or workstation cluster that provides high computing power within a limited budget. However, a cluster may consist of different types of processors and this heterogeneity within a cluster complicates the design of efficient collective communication protocols. This paper introduces a synchronous communication model where the communication cost is determined by both sender and receiver. In this synchronous model both sender and receiver of a message must wait until the current communication finishes. We show that a technique called SNF tree scheduling is an approximation algorithm with competitive ratio 4. We conduct experiments to demonstrate that SNF tree scheduling produces broadcast schedules that are very close to the optimal solutions without extensive computation time. We also propose a greedy broadcast algorithm that achieves near optimal solutions in our experiments.
Dang, Sanjeena. "Variational Approximations and Other Topics in Mixture Models". Thesis, 2012. http://hdl.handle.net/10214/3876.
Texto completoNSERC PGS-D
Lourenço, Sofia Pinheiro. "From the local density approximation to exact exchange in time-dependent density functional theory: the case of rare-gas cationic clusters". Master's thesis, 2019. http://hdl.handle.net/10316/87977.
Texto completoMediante ionização, o espectro de absorção de clusters neutras de gases raros transita da gama do ultravioleta (UV) para a gama do visível. Em time-dependent density functional theory (TDDFT) e utilizando os tradicionais funcionais para a correlação e troca (LDA, GGA), é posível fazer boas previsões para o posicionamento dos dois picos experimentais da cluster de Xe_3^+, mas a intensidade dos mesmos surge trocada, i.e. o pico experimental de maior intensidade corresponde ao pico teórico de menor intensidade e vice versa. O facto deste problema ter sido resolvido ao nível da aproximação de Hartree-Fock sugere como possível explicação para esta incapacidade preditiva da DFT a forma insatisfatória como a interação de troca é tratada nos funcionais da densidade típicos. O principal objetivo desta tese é continuar a estudar a forma como a troca exata melhora a intensidade relativa dos picos, calculando-se para tal geometrias de estado fundamental e espectros de absorção com os seguintes funcionais: LDA+ADSIC (LDA com Average Density Self-Interaction Correction), OEP-SLATER, OEP-KLI, OEP-FULL (sem aproximação ao potencial de troca). No fim, conclui-se que a aquisição das geometrias de estado fundamental corretas é necessária para a obtenção de espectros corretos, comparáveis ao experimental. Também, quanto maior a quantidade de troca incluída no funcional, melhor o espectro. Por último, não se verificou a inversão dos picos que, provavelmente, só se viria a verificar com OEP-FULL. Os espectros de absorção e as geometrias foram calculados no código open-source OCTOPUS.
Upon ionization, the optical absorption of neutral rare-gas clusters shifts from the ultraviolet range (UV) to the visible range. Within time-dependent density functional theory (TDDFT), the photoabsorption spectra of the Xe_3^+ cluster, employing traditional DFT functionals (LDA, GGA), predicts a reasonable position for the two experimental peaks, but their relative intensities appears to be inverted, i.e. the highest experimental peak correspond to the lowest theoretical peak and vice versa. The improvement on the problem reached within the Hartree-Fock approximation level suggested an explanation based on the unsatisfactory treatment of the exchange interaction in common density functionals. The main goal of this thesis project is to continue investigating on how the exact exchange improves peaks' relative height by calculating ground state geometries and absorption spectra with the following functionals: LDA+ADSIC (LDA with Average Density Self-Interaction Correction), OEP-SLATER, OEP-KLI, OEP-FULL (no approximation to the exchange-only potential). In the end, it is concluded that adequate ground state geometries are necessary for the generation of correct spectra, comparable to the experimental one. Also, the bigger the amount of exchange added, the better the spectrum, even though the peaks did not invert their intensities. At last, OEP-FULL probably is the level of theory required to invert the peaks. Absorption spectra and geometries were calculated in the open-source code OCTOPUS.