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Neste trabalho, filmes amorfos de oxinitreto de silício (alfa-SiO IND.XN IND.Y:H) foram crescidos pelo processo de Plasma Enhanced Chemical Vapor Deposition (PECVD) a temperatura da 320ºC. No processo de deposição foi utilizada a mistura dos gases óxido nitroso (N IND.2O) e silano (SiH IND.4), variando-se a razão entre os seus fluxos (Re= N2O/SiH4) num intervalo de 0,25 Re 5,00. Foram obtidos filmes com diferentes composições químicas, sendo ricos em O (65 at.%) para Re 2,00 e ricos em Si (44 at. %) para Re 1,50. A técnica de Rutherford backscattering spectroscopy (RBS) foi utilizada para determinar a composição química dos filmes. Os dados de RBS mostram um decréscimo da quantidade de O, enquanto que as quantidades de Si e N aumentam com o decréscimo de Re. A morfologia dos filmes foi estudada por Small Angell X-ray scattering (SAXS), Transmissio Electron Microscopy (TEM) e medida de densidade pelo método de flutuação. Os dados de SAXS revelam a presença de centros espalhadores com raio médio que varia de 10 Ã a 100 Ã. Os resultados de TEM mostram a presença de aglomerados esféricos dispersos numa matriz de mesmas espécies atômicas. A concentração de poros nos filmes é inferior a 10% e diminui com o aumento do conteúdo de oxigênio. Tanto a estrutura de ordem local quanto as ligações químicas foram investigadas pelas técnicas de X-ray Absorption Near Edge Structure (XANES), Extented X-ray Absorption Fine Structure (EXAFS) e Fourier Transform Infrared Spectroscopy (FTIR). foi desenvolvido um potencial modelo de interação para simular a estrutura atômica do oxinitreto de silício amorfo e compará-la com os dados experimentais. As simulações computacionais foram realizadas utilizando o método de Monte Carlo (MC)-Metropolis. A análise estrutural das amostras ricas em O, tanto do ponto de vista experimental quanto teórico (obtidos por MC), mostram que a estrutura básica da rede é um tetraedro, onde o átomo central é o Si conectado por O e N. Os resultados experimentais das amostras ricas em si, apontam para a formação de agregados de Si, embebidos dentro de uma matriz de Si-O-N. Tratamentos térmicos a vácuo em temperaturas entre 550 e 1000 ºC promovem a efusão de hidrogênio e segregação de diferentes fases. / In this work, thin films of amorphous silicon oxynitride(alfa-SiOxNy:H) were deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) at 320 ºC. In the deposition process a mixture of nitrous oxide (N2O) and silane (SiH4) was used, varying their flow ratio (Re= N2O/SiH4) in an interval of 0,25 Re 5,00. Films with different chemical composition were obtained, being O-rich (65 at.%) for Re 2,00 and Si-rich (44 at.%) for Re 1,50. The Rutherford backscattering spectroscopy (RBS) was used to determine the atomic content of the films. The RBS data showed a decrease of the oxygen content while the Si and N contents increase with the decrease of Re. The films morphology was studied by Small Angle X-ray scattering (SAXS), Transmission Electron Microscopy (TEM) and density measurements by the flotation method. The SAXS data revealed the presence of scattering centers with mean radius from 10 Ã to 100 Ã. The TEM data showed the presence of spherical clusters dispersed in a matrix of the same atomic species. The concentration of pores in the material is less than 10% and decreases with the increase of oxygen content. The local atomic structure and chemical bonds were investigated by X-ray Absorption Near Edge Structure (XANES), Extended X-ray Absorption Fine Structure (EXAFS) and Fourier Transform Infrared spectroscopy (FTIR). A model of interatomic potential was developed to simulate the atomic structure of the amorphous silicon oxynitride in order to be compared with the experimental data. The computer simulations were performed by the Monte Carlo (MC) Metropolis method. The structural analysis of the O-rich samples, obtained by both experimental and theoretical simulations (obtained by MC), showed that the basic structure of the network is tetrahedral, being Si the central atom connected by O and N. The experimental results of the Si-rich samples indicate the formation of Si aggregates, embedded in a Si-O-N matrix. Annealing in vacuum, at temperatures between 550 e 1000 ºC, promoted hydrogen effusion and segregation of different phases.

O uso de dióxidos de metais de transição em aplicações tecnológicas é bastante amplo, pois esses compostos possuem características importantes de semicondutores. Apesar de existir um grande número de estudos experimentais e teóricos, o entendimento das propriedades estruturais e eletrônicas desses compostos ainda não é satisfatória, principalmente quando se envolve o estudo de clusters. Clusters podem ser definidos como uma fase embrionária da matéria, pois são partículas contendo um número muito reduzido de átomos em comparação com partículas macroscópicas. Logo, suas propriedades estruturais e eletrônicas são totalmente distantes da fase cristalina do material, o que permite o desenvolvimento de novos materiais para aplicações tecnológicas. Portanto, existe um grande interesse em compreender as propriedades estruturais e eletrônicas dos clusters. Neste projeto de mestrado temos como objetivo estudar as propriedades estruturais e eletrônicas de clusters de TiO2 e CeO2 , usando para isso cálculos de primeiros princípios com base na teoria do funcional da densidade (DFT). Um dos principais problemas no estudo de clusters é a determinação da estrutura atômica, devido as dificuldades experimentais envolvidas em se trabalhar com estruturas tão pequenas. Dessa forma, um dos nossos maiores desafios foi a determinação das estruturas atômicas dos clusters desses dois tipos de dióxidos de metais de transição, uma vez que, o nosso grupo (QTnano) já conta com grande experiência, principalmente no desenvolvimento e implementação de algoritimos de otimização global. Devido as dificuldades envolvidas no estudo de partículas tão pequenas, ficamos restritos ao estudo de clusters com composição (MO2)n , com n = 1-15, ou seja, os nossos maiores clusters tem um total de 45 átomos, formando estruturas com diâmetro de inferior a 3 nm. Além da obtenção das estruturas, foi realizado o estudo das propriedades eletrônicas, energéticas e vibracionais para cada uma das composições geradas, o que propiciou a melhor compreensão sobre os efeitos eletrônicos nas estrutura atômica dos clusters. / The use of transition metal dioxides in technological applications is wide spread, because these compounds have important characteristics of semiconductors. Although there a large number of theoretical and experimental studies, the acknowledgement about the structural and electronic properties these compounds are not yet satisfactory, especially when studying clusters. Clusters can be defined as an embryonic phase of matter, because they are particles that contain a very small number of atoms in comparison with macroscopic particles. So, the structural and electronic properties are very distinct of the material crystalline phase, when allow the development of new materials in technological applications. Therefore a large interest exist in understanding the structural and electronic properties of clusters. In this master\'s degree project we have as objective to study the electronic and structural properties of TiO2 and CeO2 clusters, using first principle calculations based on the density functional theory (DFT). One of the main problems in the study of clusters is to determine the atomic structure, due the experimental difficult of work with so small particles. Thus, a great challenge was to determine the atomic structures of these two different transition metal dioxides, considering that our group (QTnano), has a large knowledge in the development and implementation of global optimization algorithms. Due the difficulty involved in studying small particles, we were restricted to the clusters of composition (MO2)n, with n = 1-15. In other words, our largest clusters have 45 atoms and a diameter smaller than 3 nm. Along with securing the structures, we realize the study of electronic, energetic and vibrational properties to each generated composition, providing an understanding of electronic effects in the atomic structure of clusters.

Neste trabalho, filmes amorfos de oxinitreto de silício (alfa-SiO IND.XN IND.Y:H) foram crescidos pelo processo de Plasma Enhanced Chemical Vapor Deposition (PECVD) a temperatura da 320ºC. No processo de deposição foi utilizada a mistura dos gases óxido nitroso (N IND.2O) e silano (SiH IND.4), variando-se a razão entre os seus fluxos (Re= N2O/SiH4) num intervalo de 0,25 Re 5,00. Foram obtidos filmes com diferentes composições químicas, sendo ricos em O (65 at.%) para Re 2,00 e ricos em Si (44 at. %) para Re 1,50. A técnica de Rutherford backscattering spectroscopy (RBS) foi utilizada para determinar a composição química dos filmes. Os dados de RBS mostram um decréscimo da quantidade de O, enquanto que as quantidades de Si e N aumentam com o decréscimo de Re. A morfologia dos filmes foi estudada por Small Angell X-ray scattering (SAXS), Transmissio Electron Microscopy (TEM) e medida de densidade pelo método de flutuação. Os dados de SAXS revelam a presença de centros espalhadores com raio médio que varia de 10 Ã a 100 Ã. Os resultados de TEM mostram a presença de aglomerados esféricos dispersos numa matriz de mesmas espécies atômicas. A concentração de poros nos filmes é inferior a 10% e diminui com o aumento do conteúdo de oxigênio. Tanto a estrutura de ordem local quanto as ligações químicas foram investigadas pelas técnicas de X-ray Absorption Near Edge Structure (XANES), Extented X-ray Absorption Fine Structure (EXAFS) e Fourier Transform Infrared Spectroscopy (FTIR). foi desenvolvido um potencial modelo de interação para simular a estrutura atômica do oxinitreto de silício amorfo e compará-la com os dados experimentais. As simulações computacionais foram realizadas utilizando o método de Monte Carlo (MC)-Metropolis. A análise estrutural das amostras ricas em O, tanto do ponto de vista experimental quanto teórico (obtidos por MC), mostram que a estrutura básica da rede é um tetraedro, onde o átomo central é o Si conectado por O e N. Os resultados experimentais das amostras ricas em si, apontam para a formação de agregados de Si, embebidos dentro de uma matriz de Si-O-N. Tratamentos térmicos a vácuo em temperaturas entre 550 e 1000 ºC promovem a efusão de hidrogênio e segregação de diferentes fases. / In this work, thin films of amorphous silicon oxynitride(alfa-SiOxNy:H) were deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) at 320 ºC. In the deposition process a mixture of nitrous oxide (N2O) and silane (SiH4) was used, varying their flow ratio (Re= N2O/SiH4) in an interval of 0,25 Re 5,00. Films with different chemical composition were obtained, being O-rich (65 at.%) for Re 2,00 and Si-rich (44 at.%) for Re 1,50. The Rutherford backscattering spectroscopy (RBS) was used to determine the atomic content of the films. The RBS data showed a decrease of the oxygen content while the Si and N contents increase with the decrease of Re. The films morphology was studied by Small Angle X-ray scattering (SAXS), Transmission Electron Microscopy (TEM) and density measurements by the flotation method. The SAXS data revealed the presence of scattering centers with mean radius from 10 Ã to 100 Ã. The TEM data showed the presence of spherical clusters dispersed in a matrix of the same atomic species. The concentration of pores in the material is less than 10% and decreases with the increase of oxygen content. The local atomic structure and chemical bonds were investigated by X-ray Absorption Near Edge Structure (XANES), Extended X-ray Absorption Fine Structure (EXAFS) and Fourier Transform Infrared spectroscopy (FTIR). A model of interatomic potential was developed to simulate the atomic structure of the amorphous silicon oxynitride in order to be compared with the experimental data. The computer simulations were performed by the Monte Carlo (MC) Metropolis method. The structural analysis of the O-rich samples, obtained by both experimental and theoretical simulations (obtained by MC), showed that the basic structure of the network is tetrahedral, being Si the central atom connected by O and N. The experimental results of the Si-rich samples indicate the formation of Si aggregates, embedded in a Si-O-N matrix. Annealing in vacuum, at temperatures between 550 e 1000 ºC, promoted hydrogen effusion and segregation of different phases.

O uso de dióxidos de metais de transição em aplicações tecnológicas é bastante amplo, pois esses compostos possuem características importantes de semicondutores. Apesar de existir um grande número de estudos experimentais e teóricos, o entendimento das propriedades estruturais e eletrônicas desses compostos ainda não é satisfatória, principalmente quando se envolve o estudo de clusters. Clusters podem ser definidos como uma fase embrionária da matéria, pois são partículas contendo um número muito reduzido de átomos em comparação com partículas macroscópicas. Logo, suas propriedades estruturais e eletrônicas são totalmente distantes da fase cristalina do material, o que permite o desenvolvimento de novos materiais para aplicações tecnológicas. Portanto, existe um grande interesse em compreender as propriedades estruturais e eletrônicas dos clusters. Neste projeto de mestrado temos como objetivo estudar as propriedades estruturais e eletrônicas de clusters de TiO2 e CeO2 , usando para isso cálculos de primeiros princípios com base na teoria do funcional da densidade (DFT). Um dos principais problemas no estudo de clusters é a determinação da estrutura atômica, devido as dificuldades experimentais envolvidas em se trabalhar com estruturas tão pequenas. Dessa forma, um dos nossos maiores desafios foi a determinação das estruturas atômicas dos clusters desses dois tipos de dióxidos de metais de transição, uma vez que, o nosso grupo (QTnano) já conta com grande experiência, principalmente no desenvolvimento e implementação de algoritimos de otimização global. Devido as dificuldades envolvidas no estudo de partículas tão pequenas, ficamos restritos ao estudo de clusters com composição (MO2)n , com n = 1-15, ou seja, os nossos maiores clusters tem um total de 45 átomos, formando estruturas com diâmetro de inferior a 3 nm. Além da obtenção das estruturas, foi realizado o estudo das propriedades eletrônicas, energéticas e vibracionais para cada uma das composições geradas, o que propiciou a melhor compreensão sobre os efeitos eletrônicos nas estrutura atômica dos clusters. / The use of transition metal dioxides in technological applications is wide spread, because these compounds have important characteristics of semiconductors. Although there a large number of theoretical and experimental studies, the acknowledgement about the structural and electronic properties these compounds are not yet satisfactory, especially when studying clusters. Clusters can be defined as an embryonic phase of matter, because they are particles that contain a very small number of atoms in comparison with macroscopic particles. So, the structural and electronic properties are very distinct of the material crystalline phase, when allow the development of new materials in technological applications. Therefore a large interest exist in understanding the structural and electronic properties of clusters. In this master\'s degree project we have as objective to study the electronic and structural properties of TiO2 and CeO2 clusters, using first principle calculations based on the density functional theory (DFT). One of the main problems in the study of clusters is to determine the atomic structure, due the experimental difficult of work with so small particles. Thus, a great challenge was to determine the atomic structures of these two different transition metal dioxides, considering that our group (QTnano), has a large knowledge in the development and implementation of global optimization algorithms. Due the difficulty involved in studying small particles, we were restricted to the clusters of composition (MO2)n, with n = 1-15. In other words, our largest clusters have 45 atoms and a diameter smaller than 3 nm. Along with securing the structures, we realize the study of electronic, energetic and vibrational properties to each generated composition, providing an understanding of electronic effects in the atomic structure of clusters.

Orientação: Pedro Faria dos Santos Filho / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-24T01:23:37Z (GMT). No. of bitstreams: 1 Baptista_ManuelMoreira_D.pdf: 2828376 bytes, checksum: 50c4bde045ccee91fe0ce93a176d51de (MD5) Previous issue date: 2013 / Resumo: As animações deste trabalho foram desenvolvidas utilizando o software Blender®. Este software, de código aberto e gratuito, é atualmente um dos recursos computacionais mais avançados para modelagem e animação em 3D. As animações foram planejadas para serem usadas em sala de aula e, portanto, são desprovidas de narração e legenda. Os assuntos contemplados foram: Teoria do Orbital Atômico, distribuição eletrônica, hibridização, Teoria do Orbital Molecular, Teoria de Ligação de Valência, Teoria VSEPR, estruturas de Lewis, estruturas cristalinas dos compostos iônicos e metais (cela unitária, empacotamento e retículo cristalino), transformações químicas e polímeros. As animações de maior interesse estão relacionadas com a teoria do orbital atômico e molecular. As animações foram avaliadas no IQ-UNICAMP através de questionários respondidos pelos alunos da disciplina de pós-graduação QP443, e pelos alunos da disciplina de graduação QG101. No questionário da disciplina QP443, procurouse descobrir o planejamento que o professor deve fazer para inserir as animações em uma aula tradicional. No questionário da disciplina QG101, procurou-se avaliar a contribuição que as animações podem dar para o ensino-aprendizado de Química em aulas presenciais. As animações também foram avaliadas através das informações fornecidas pela estatística dos websites www.quimica3d.com e www.youtube.com/user/m770596. As respostas dos questionários aplicados nas disciplinas QG101 e QP443 permitem-nos concluir que as animações facilitaram a visualização tridimensional e estimularam o desenvolvimento da capacidade de abstração dos alunos. As informações da estatística do canal www.youtube/user/m770596 e do website www.quimica3d.com mostram que houve grande interesse pelas animações. / Abstract: The animations of this work were developed using the Blender ® software. This free and open-source software is currently one of the most advanced computing resources for 3D modeling and animation. The animations were designed for classroom application and for this reason they have no narration and subtitles. The topics covered were: Atomic Orbital Theory, electronic distribution, hybridization, Molecular Orbital Theory, Valence Bond Theory, VSEPR Theory, Lewis structures, crystal structure of ionic compounds and metals (unit cell, packing and crystal lattice), chemical transformations and polymers. The animations of most interest are related to atomic and molecular orbital theory. The animations were valued at the IQ-UNICAMP through questionnaires answered by the QP443 discipline postgraduate students, and by the QG101 discipline undergraduate students. In the questionnaire of the QP443 discipline, we intended to find the schedule that the teacher should use to insert the animations in a traditional classroom. In the questionnaire of the QG101 discipline, we intended to evaluate the contribution of the animations to Chemistry teaching and learning in classroom. The animations were also valued through the information given by the statistics of the www.youtube.com/user/m770596 YouTube channel and www.quimica3d.com website. The answers from the questionnaires of the QG101 and QP443 disciplines allowed us to conclude that the three-dimensional visualization animations facilitated and stimulated the development of students' capacity for abstraction. The statistical information from the www.youtube/user/m770596 YouTube channel and www.quimica3d.com website showed that there was great interest for the animations. / Doutorado / Quimica Inorganica / Doutor em Ciências

The research presented in this thesis concerns experimental studies of thin manganese silicide and germanide layers, grown by solid phase epitaxy on the Si(111)7×7 and the Ge(111)c(2×8) surfaces, respectively. The atomic and electronic structures, as well as growth modes of the epitaxial Mn-Si and Mn-Ge layers, were investigated by low-energy electron diffraction (LEED), angle-resolved photoelectron spectroscopy (ARPES), core-level spectroscopy (CLS), and scanning tunneling microscopy and spectroscopy (STM and STS). The magnetic properties of the Mn-Ge films were investigated by X-ray magnetic circular dichroism (XMCD). The Mn-Si layers, annealed at 400 °C, showed a √3×√3 LEED pattern, consistent with the formation of the stoichiometric monosilicide MnSi. Up to 4 monolayers (ML) of Mn coverage, island formation was observed. For higher Mn coverages, uniform film growth was found. Our results concerning morphology and the atomic and electronic structure of the Mn/Si(111)-√3×√3 surface, are in good agreement with a recent theoretical model for a layered MnSi structure and the √3×√3 surface structure. Similar to the Mn-Si case, the grown Mn-Ge films, annealed at 330 °C and 450 °C, showed a √3×√3 LEED pattern. This indicated the formation of the ordered Mn5Ge3 germanide. A strong tendency to island formation was observed for the Mn5Ge3 films, and a Mn coverage of about 32 ML was needed to obtain a continuous film. Our STM and CLS results are in good agreement with the established model for the bulk Mn5Ge3 germanide, with a surface termination of Mn atoms arranged in a honeycomb pattern. Mn-Ge films grown at a lower annealing temperature, 260 °C, showed a continuous film at lower coverages, with a film structure that is different compared to the structure of the Mn5Ge3 film. XMCD studies showed that the low-temperature films are ferromagnetic for 16 ML Mn coverage and above, with a Curie temperature of ~250 K.

Abstract In this thesis electronic structure of atomic chromium, rubidium and bromine are studied experimentally and theoretically through transitions and decay processes originating from selected M-shell hole states. The experiments are conducted with traditional methods of electron spectroscopy as well as more recent multicoincidence methods using pulsed synchrotron radiation and a magnetic bottle spectrometer. The observed electronic transitions are theoretically simulated with multiconfiguration Dirac-Fock method. Finally, the calculations are used to interpret the measured spectra to investigate the energy level structure and electron dynamics of the studied elements. / Original papers Original papers are not included in the electronically distributed version of the thesis. Keskinen, J., Huttula, S.-M., Mäkinen, A., Patanen, M., & Huttula, M. (2015). Experimental and theoretical study of 3p photoionization and subsequent Auger decay in atomic chromium. Radiation Physics and Chemistry, 117, 209–216. https://doi.org/10.1016/j.radphyschem.2015.08.018 Keskinen, J., Lablanquie, P., Penent, F., Palaudoux, J., Andric, L., Cubaynes, D., … Jänkälä, K. (2017). Initial-state-selected MNN Auger spectroscopy of atomic rubidium. Physical Review A, 95(4). https://doi.org/10.1103/physreva.95.043402 http://jultika.oulu.fi/Record/nbnfi-fe201706207380 Keskinen, J., Jänkälä, K., Huttula, S.-M., Kaneyasu, T., Hikosaka, Y., Shigemasa, E., … Lablanquie, P. (2019). Auger decay of the 3d hole in the isoelectronic series of Br*, Kr⁺ and Rb²⁺. Manuscript in preparation.

Proteins are involved in almost all functions in a living cell, and functions of proteins are realized by their tertiary structures. Protein three-dimensional structures can be solved by multiple experimental methods, but computational approaches serve as an important complement to experimental methods for comparing and analyzing protein structures. Protein structure comparison allows the transfer of knowledge about known proteins to a novel protein and plays an important role in function prediction. Obtaining a global perspective of the variety and distribution of protein structures also lays a foundation for our understanding of the building principle of protein structures. This dissertation introduces our computational method to compare protein 3D structures and presents a novel mapping of protein shapes that represents the variety and the similarities of 3D shapes of proteins and their assemblies. The methods developed in this work can be applied to obtain new biological insights into protein atomic structures and electron density maps.

Les alliages métalliques complexes (CMAs) sont des composés intermétalliques dont la structure cristallographique diffère des alliages habituels par le nombre conséquent d'atomes dans la cellule unitaire et par l'occurrence d'agrégats de haute symétrie comme briques élémentaires. La structure spécifique des CMAs leur confère des propriétés physico-chimiques originales par rapport aux alliages métalliques plus classiques, en particulier ce qui concerne les propriétés de surface. L'objet de cette thèse est la détermination de la structure atomique et électronique de surfaces d'alliages métalliques complexes à base d'aluminium et cobalt par des méthodes de calcul ab initio basées sur la théorie de la fonctionnelle de la densité. Plusieurs alliages de complexités différentes ont été considérés : Al5Co2, Al9Co2 et o-Al13Co4. Les résultats des calculs réalisés dans ce travail sont confrontés aux données expérimentales.Le manuscrit comporte trois parties. La première partie porte sur les méthodes numériques utilisées. La deuxième partie porte sur l'étude des surfaces nues. Un modèle structural est proposé pour la terminaison des surfaces (001) de Al9Co2 et (100) de o-Al13Co4, qui consiste en un plan dense, riche en aluminium, obtenu par troncature du système massif. Ce résultat est en bon accord avec ce qui a été observé dans le cas des quasicristaux, qui sont un cas particulier de CMAs. Cette étude montre également que pour toutes les surfaces étudiées, la présence d'atomes de cobalt en surface est défavorable. La nature quasi covalente de certaines liaisons présentes dans les CMAs étudiés joue également un rôle fondamental dans la sélection du plan de surface.La troisième partie de ce travail porte sur l'étude de l'adsorption de plomb et d'oxygène atomique sur les surfaces (001) de Al9Co2 et (100) de o-Al13Co4. L'étude réalisée révèle que les atomes de cobalt en surface et en sous-surface exercent une influence sur la détermination des sites d'adsorption préférentiels. La relaxation des atomes du substrat est importante dans le cas de l'adsorption d'oxygène atomique. Les distances Al-O calculées correspondent aux distances typiques d'adsorption d'oxygène atomique à la surface (111)Al, ainsi qu'aux distances Al-O dans l'oxyde Al2O3. Dans le cas de l'adsorption de plomb sur (100)o-Al13Co4, les premières étapes vers la formation d'un film pseudomorphique ont été simulées / Complex metallic alloys (CMAs) are intermetallic compounds whose crystal structure differs from the usual alloys by the number of atoms in the unit cell and the occurrence of high symmetry aggregates as building blocks. The specific structure of CMAs gives them unique physical and chemical properties compared to more conventional metallic alloys, particularly with regard to surface properties.The overall goal of this thesis is the determination of the atomic and electronic surface structure of alumnium-cobalt based complex metal alloys using ab initio calculation methods based on the density functional theory. Several alloys of different complexity were considered: Al5Co2, Al9Co2 and o-Al13Co4. The calculation results of this work are confronted with experimental data.The present manuscript contains three parts. The first part deals with numerical methods. The second part deals with the study of clean surfaces. A structural model is proposed for the termination of the (001)Al9Co2 and (100)o-Al13Co4 surfaces, which consist in a dense aluminum rich plan obtained by bulk truncation. This result is in good agreement with what is observed in the case of quasicrystals – a special case of CMAs. This study also shows that for all surfaces studied, the presence of cobalt atoms on the surface is unfavoured. The quasi-covalent bonds present in the studied CMAs plays a fundamental role in the selection of the surface plane.The third part of this work deals with the adsorption of lead and oxygen atoms on the (001)Al9Co2 and (100)o-Al13Co4 surfaces. The study reveals that the surface and subsurface cobalt atoms influence on the determination of the preferential adsorption sites. The substrate atomic relaxation is important in the case of atomic oxygen adsorption. The calculated Al-O distances correspond to typical atomic oxygen adsorption distances on the (111)Al surface and with the Al-O distances in the Al2O3 oxide. In the case of atomic lead adsorption on the (100)o-Al13Co4 surface, the first step towards the formation of a pseudomorphic film was simulated