INFORME FINAL"Alguns importants descobriments de la ciència són accidentals. Això fou, certament, el cas del ful·lerè C60. Quan ara fa quatre anys, l'any 2000, vaig iniciar el treball d'investigació sobre els metal·loful·lerens m'havien arribat veus de la importància mediàtica d'aquestes noves estructures però no de la intensa història del seu descobriment. Aquesta m'ha fascinat. Sobretot quan l'any 2003 vaig tenir la possibilitat de fer una estada al grup del professor Kroto de la universitat de Sussex (Gran Bretanya). Llavors els textos, sorprenents però inerts, que havia llegit sobre la història del descobriment dels ful·lerens prenien forma en espais coneguts i personatges propers". Aquest és el prefaci de la meva tesi. Segurament aquesta estada a Sussex al grup d'un dels descobridors dels ful·lerens ha estat el moment més entranyable en aquesta carrera científica per l'estudi dels metal·loful·lerens.A partir de la síntesi de la molècula de C60 en quantitats apreciables la química dels ful·lerens en general, i en particular amb metalls de transició, ha experimentat un increment espectacular. L'objectiu d'aquesta tesi és l'estudi de l'estructura i la reactivitat de diferents derivats organometàl·lics de ful·lerens o metal·loful·lerens. El treball d'investigació usa les eines de la química computacional (Teoria del funcional de la densitat, DFT) per tal de modelar els metal·loful·lerens més interessants apareguts entre el 1999 i el 2005. Tot i que els metal·loful·lerens presenten una varietat d'estructures formidable, podem classificar-los en tres grans famílies des del punt de vista estructural: un primer grup són els metal·loful·lerens exoèdrics on els metalls es situen fora de la caixa, en un segon grup tenim els metal·loful·lerens heteroèdrics o heteroful·lerens on les caixes de carbonis han estat dopades (certes posicions han estat substituïdes) amb altres elements com ara: N, B, Si, Fe i altres metalls i finalment l'últim grup són els metal·loful·lerens endoèdrics on la derivatització metàl·lica es dóna a l'interior de la caixa. Així l'estudi teòric dels compostos més novedosos i novells de cadascuna de les tres famílies de metal·loful·lerens és el puntal de la present tesi doctoral. Per cadascuna de les famílies hem desgranat l'estructura electrònica i geomètrica, hem descrit el tipus d'enllaç metall-ful·lerè, hem avaluat els factors que intervenen en l'estabilitat relativa dels possibles isòmers, hem també predit la reactivitat davant de reaccions d'addició i finalment els hem caracteritzat des d'un punt de vista físic (càlcul del potencial d'ionització i afinitat electrònica). L'estructura electrònica ens ha permès seleccionar quins metal·loful·lerens endoèdrics seran estables avançant-nos als experimentalistes en la seva cerca de nous complexos. La diversitat de tipologies d'enllaç ha sigut tant gran com famílies de metal·loful·lerens. Hem descrit un enllaç iònic pels metal·loful·lerens endoèdrics, un enllaç covalent en el cas dels metal·loful·lerens heteroèdrics i un enllaç coordinatiu pels metal·loful·lerens exoèdrics. Hem aplicat noves metodologies per l'estudi de l'isomerisme. Les tècniques d'anàlisi multivariant de dades ens han permès esbrinar quins factors són importants per l'estabilitat relativa dels isòmers i a la vegada construir models de predicció per altres isòmers. Així doncs, l'acoblament de la química teòrica i la quimiometria ha estat sens dubte l'aportació més rellevant del present treball d'investigació.Tarragona, 28 de novembre de 2004Josep Maria Campanera AlsinaFINAL REPORT The characterisation of the most novel metallofullerenes up to 2004 has been theoretically and systematically discussed in this study. From the structural point of view, metallofullerenes can be divided into three main groups, all of which have been discussed in this study: endohedral, heterohedral and exohedral metallofullerenes. The main families of compounds studied are Sc3-nMnN@Ck (n = 0-3, M = Y, La; k = 68, 78, 80) (endohedral), CxMn (x = 56, 57, 58, 59; M = Pt, Ir, Os; n = 1, 2) (heterohedral) and (-Ck){M(PH3)2}n (k = 60, 70, 84; M = Pt, Pd, Ni; n = 1, 2, 4, 6) (exohedral). The present study is a step forward in our knowledge of each of these families of compounds, and in particular, in our understanding of the metal-carbon bond, isomerism and reactivity. The DFT method proved to be an excellent computational tool for providing good geometries, for solving the intricacies of the different metal-carbon bonds, for producing experimental data (ionization potentials and electron affinities) and also for making predictions about isomerism stability and reactivity. The principal conclusions drawn about the species studied here are: Different types of structures, different types of metal-carbon bonds. The metal units in each family of compounds are located differently in relation to the fullerene carbon framework: inside the cage, within the carbon framework and outside the cage. The encapsulation of a trimetallic nitride template unit (TNT, Sc3-nMnN; n = 0-3; M = Y, La) inside the carbon cage to produce TNT endohedral metallofullerenes is explained by an ionic pair (cage-metal) model in which the TNT unit formally transfers six electrons to the cage. On the other hand, in heterohedral metallofullerenes, metals establish a covalent metal-carbon bond without causing oxidation to the metal. Finally, the (MPH3)2 metal units situated exohedrally to the fullerene are only coordinated in a  mode to the CC bond. Chemometric tools applied to isomerism studies. The regioisomers of heterohedral metallofullerenes are numerous: for example, the stoichiometry C57Pt2 has 47 distinct regioisomers. Thus, chemometric techniques which can manage considerable amounts of data must be used if we want to understand regioisomerism in heterohedral metallofullerenes. These tools have also been very useful for drawing conclusions from the considerable quantities of data provided by the factors which affect the stability of regioisomers. These tools have been used not only for analysing data but also for predicting the stability of other heterofullerenes.TNT encapsulation stabilizes fullerene isomers that are not available as free fullerenes. TNT endohedral metallofullerenes are formed by the encapsulation of a metallic nitride template inside the following cages: D3-C68:6140, D3h'-C78:5, D5h-C80:6 and Ih-C80:7. Any of these cages have never been detected experimentally.So, endohedral metallofullerenes can make non-classical fullerene isomers available for study. Furthermore, on the basis of the electronic structure we predicted that no other IPR fullerenes between C60 and C84 will be capable of encapsulating a TNT unit, apart from the fullerene isomers that are already known.Stability of the carbon skeleton is the principal factor that determines the regioisomer stability of the heterofullerenes. Metal atoms occupy neighbouring positions in the most stable structures of C57Pt2 and C56Pt2. Metal substitution deforms the carbon framework and partially destroys the fullerene aromaticity. This is the key factor in determining the stability of these disubstituted clusters. Indeed, it is much easier to make a big hole that permits the incorporation of two Pt atoms in the carbon cage than two smaller holes in two opposite sites of the fullerene. Prediction of the exohedral reactivity taking into account the full characterization of the different CC bond types. We first performed a full characterization of all CC bond types of the fullerenes Ih-C60:1, D3-C68:6140, D5h-C70:1, D3h'-C78:5, Ih-C80:7, D2-C84:22 and D2d-C84:23. Each CC bond type is characterized by its topology, length, pyramidalization angle and Mayer bond order. This systematization enabled us to identify which sites were most reactive to a nucleophilic addition to free fullerenes or a [4 + 2] cycloaddition to TNT endohedral metallofullerenes.Tarragona, 8th Novembre 2004Josep Maria Campanera Alsina

The detection of gamma-rays is an important issue in a cast array ofindustries. CdTe is a semiconductor used for gamma-ray detectors whichcan operate at high temperatures. Density functional theory calculationsof the electronic structure within the Perdew-Burke-Ernzerhof exchange-correlation functional underestimate the bandgap of CdTe: the calculatedbandgap within PBE is less than half the experimental value. The useof a hybrid functional approach to exchange and correlation describes thebandgap correctly. The goal of this project was to nd out if PBE calcu-lations give an adequate description of defects in CdTe by comparing it tohybrid functional calculations. We show that PBE is adequate in describ-ing Te antisite defects in CdTe if a correction to the bandgap is applied.The defect level for both PBE and hybrid functional was calculated to be0.24 eV above the valance band.

This thesis focus on the magnetic behavior, from single atoms to bulk materials. The materials considered in this thesis have been studied by computational methods based on ab initio theory, density functional theory (DFT), including treatment of the spin-orbit coupling, non-collinear magnetism, and methods capable of treating discorded systems. Furthermore strongly correlated materials have been investigated using the dynamical mean field theory (DMFT). The uniaxial magnetic anisotropy energy (MAE) of the Fe2P was investigated using the full-potential linear muffin tin orbital (FP-LMTO) method. Based on a band structure analysis, the microscopical origin of the large magnetic anisotropy found for this system is explained. It is also shown that by straining the crystal structure, the MAE can be enhanced further. This opens up for the possibility of obtaining a room temperature permanent magnet based on the Fe2P. The spectral properties of Fe impurities in a Cs host have been investigated, for both surface and bulk systems, by means of combination of density-functional theory in the local density approximation and the dynamical mean-field theory (LDA+DMFT), using two different impurity solvers, the Hubbard I approximation (HIA) and the Exact Diagonalization (ED) method were used. It is shown that noticeable differences can be seen in the unoccupied part of the spectrum for different positions of Fe atoms inside the host. The calculations show good agreement with the experimental photoemission spectra. The stability of the 12-fold metal-phosphorous coordination, existing in the meteorite mineral melliniite has been investigated trough total energy calculations using the coherent potential approximation (CPA) combined with an analysis of the chemical bonds, performed by balanced crystal overlap population (BCOOP). It was shown that its uniquely high metal–phosphorous coordination is due to a balance between covalent Fe–P binding, configurational entropy and a weaker nickel–phosphorus binding. Supported clusters have drawn a lot of attention as possible building blocks for future data storage applications. This topic was investigated using a real space noncollinear formalism where the exchange interactions between Co atoms were shown to be tuned by varying the substrate surface composition. Furthermore the spin dynamics of small Co clusters an a Cu(111) surface have been investigated and a new kind of dynamics, where magnetization switching can be accelerated by decreasing the switching field, has been found. A method for calculating the electronic structure for both ordered and disordered alloys, the augmented space recursion (ASR) method, have been extended to treat non-collinear magnetic order. The method has been used to investigate the energy stability of non-collinear arrangements of MnPt and Mn3Rh alloys.

Singlet fission is a multiple-exciton-generation process found in organic materials that could help to enhance the efficiency of future photovoltaic devices, by overcoming the Shockley-Queisser limit. In spite of considerable experimental and theoretical attention, different aspects of the process are still not fully understood. The main reason for this is that singlet fission is characterised by a complex interplay of electronic states, vibrational modes and electrostatic screening effects. In this thesis we employ \emph{ab initio} electronic structure techniques to study the excitations involved in fission in molecular crystals and dimers, using the well-studied pentacene molecule as a reference system. Linear-scaling density functional theory (LS-DFT) is used to model the influence of the crystal environment on charge-transfer (CT) configurations in the pentacene molecular crystal. We derive a general dipole correction scheme that allows us to eliminate finite-size effects from the calculations. We find that CT energies are significantly lowered by the response of the crystal environment, bringing them close to the energies of local excitations. This result lends support to the idea that the photoexcited precursor state to fission has significant CT character, and emphasises the role played by CT configurations in fission in the crystal. Furthermore, we use DFT to parametrise a linear vibronic coupling Hamiltonian of a covalent dimer of pentacene, forming the basis for many-body quantum dynamics calculations of the interplay between electronic and vibrational degrees of freedom. This reveals an interesting role for symmetry in fission in such dimers. Due to their high symmetry, couplings that could enable fission are precluded at the ground-state geometry. However, dynamic symmetry breaking by vibrational modes opens up an efficient pathway for fission, via an avoided crossing mediated by virtual CT configurations. Finally, we explore the influence of different side-groups and solvent environments on fission in pentacene dimers. To this end, we employ DFT with both implicit and explicit solvent models, combined with large-scale calculations to achieve sufficient sampling of solvent-solute configurations.

Orientador: João Manuel Marques Cordeiro / Resumo: Com a constante busca o avanço tecnológico para satisfazer as necessidades da nossa sociedade, verifica-se uma preocupação da sociedade com menor degradação do meio ambiente. Em função disso, busca-se um melhor aproveitamento dos recursos naturais, o que, por sua vez, requer tecnologia apropriada. Na indústria optoeletrônica, a utilização de materiais com propriedades ópticas e condutoras cresce continuamente, porém esta tecnologia está fortemente baseada em óxido de índio (In2O3), que é um material bastante caro, já que é naturalmente escasso. Apresente pesquisa pretende contribuir com o conhecimento, em nível microscópio, das propriedades que governam a condutividade de óxidos de chumbo e óxidos de titânio dopados visando sua utilização como óxido transparente condutor, já que titânio e chumbo são mais baratos que o índio. Estudou-se propriedades eletrônicas de filmes finos de dióxido de titânio (TiO2) e dióxido de chumbo (PbO2) em sua principal fase cristalográfica, a fase rutila, em função da superfície exposta, Empregou-se cálculos ab initio dentro da teoria do funcional de densidade (DFT) implementada no programa CRYSTAL14. Procurou-se entender os fatores responsáveis pela condutividade desses materiais e formular propostas que contribuam para a transformação desses materiais em óxidos condutores transparentes. / Mestre

The spectroscopic analysis of cellulose is experimentally challenging while computationally accessible with recent developments in NMR code. However, prior to using density functional theory to calculate the NMR chemical shifts of cellulose, smaller, sugar-like molecule systems need to be benchmarked against experimental values. The quantum mechanical / molecular mechanical (QM/MM) calculations presented herein utilize six test systems: ethanol, pyridine, pyrrolidine, pyrrole, myo-inositol and scyllo-inositol in conjunction with the reference tetramethylsilane used to scale the calculated isotropic shielding tensors to relative chemical shifts. The effect of solvent on calculated NMR chemical shifts has also been investigated with regard to quantity of solvent surrounding the molecule of interest. Lastly, a mixed basis approach with two quantum regions has additionally been employed to investigate the effects of the number of basis functions on the relative cost of QM/MM NMR calculations.

Made available in DSpace on 2014-06-12T23:02:56Z (GMT). No. of bitstreams: 2 arquivo9257_1.pdf: 1343708 bytes, checksum: ca99450d2b84400468c5b975b161c84c (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2007 / Neste trabalho, cálculos de estrutura eletrônica foram utilizados para o estudo dos fatores espaciais e eletrônicos que governam a diastereoseletividade na interação de catalisadores de ródio com monoterpenos, em particular o β-pineno. A interação do catalisador com o substrato, bem como a reação de inserção do monoterpeno na ligação metal-hidreto foram analisadas utilizando como espécies catalíticas os catalisadores do tipo [HRh(CO)3] e [HRh(CO)2PMe3]. A teoria do funcioanal da densidade foi utilizada, empregando o funcional GGA-BP86. Este funcional foi escolhido após um estudo sistemático de uma reação modelo onde avaliamos as energias envolvidas na reação de inserção do etileno na ligação Rh-H do composto [Rh(CO)3(H)(C2H2)]. Através deste estudo sistemático vimos que, entre os funcionais de troca-correlação, os melhores resultados foram obtidos com os funcionais BP86, B3P86 e PBE que tiveram uma boa concordância com os cálculos CCSD(T)//CISD. Foi visto que os cálculos utilizando teoria de perturbação não funcionam para este tipo de sistema, mostrando uma flutuação muito grande na série perturbativa e apresentando resultados em completo desacordo com os resultados DFT, CISD e CCSD(T). Entretanto, os resultados MP2 e MP3 melhoram significativamente quando o procedimento de escalonamento das contribuições dos elétrons de mesmo spin e de spin contrários é utilizado. Os cálculos DFT relatados neste trabalho revelaram que a diastereoseletividade encontrada na hidroformilação do β-pineno usando o catalisador não-modificado é devido a uma combinação de dois fatores: (i) uma baixa energia de ativação no ataque pela face top que é a mais impedida estericamente, e (ii) a alta estabilidade do composto metal-alquil formado. A análise da natureza das interações metal-ligante nos revelou ainda que a coordenação pela face mais impedida da olfina gera um composto metal-alqueno que possui uma energia de interação mais forte. A substituição de um ligante CO por uma fosfina (PMe3) que é um ligante mais básico, não modifica apreciavelmente os resultados encontrados

Porous materials have application in adsorption based processes due to their high internal surface area and tailorable pore size. They find uses in fields such as catalysis, separation, biotechnology, and microelectronics. Fluids confined in such materials exhibit interesting behavior in regards to the condensation and evaporation mechanisms. Understanding study the behavior of fluids confined in these porous materials is necessary for the efficient design of these materials. The adsorption/desorption isotherm provides valuable information about the effect of network features like pore connectivity and pore size distribution on fluid behavior during pore condensation and evaporation. Such insight can be useful in the characterization of these porous materials. Three dimensionally ordered mesoporous (3DOm) carbon is a porous material that has recently emerged and is of interest. These porous structures are obtained from templating colloidal crystals formed from lysine-silica nanoparticles. The resulting structure consist of spherical pores connected to each other by windows. Due to the use of silica nanoparticles a range of tunable pore sizes can be obtained. These structures have high degree of order. They find applications in the synthesis of zeolites due to their highly controllable pore size. Hence a study of the adsorption properties of these structures is of importance. Molecular modeling has proved effective in the study of porous materials. The development of the density functional theory (DFT) and the dynamic mean field theory (DMFT) has led to great advances in the study of the behavior of confined fluids. The DFT enables the study of the adsorption desorption hysteresis phenomena of confined fluids. The DMFT describes the density profile versus time for a step change in relative pressure on the isotherm. These theories have been applied in the past to two dimensional model pore networks to investigate the mechanisms of adsorption and desorption. In this research project we aim to apply the same to various model 3DOm carbon pore networks. Studying the density distributions in these networks can help understand the thermodynamics of fluid adsorption and desorption in these structures. The results could be useful in understanding the effect of pore structure features like pore size and windows on adsorption and desorption. Also the effect of disorder in the pore network as well as effect of variation in pore size on fluid behavior can be studied. Study of the dynamics of adsorption gives an insight into the nucleation mechanisms that govern the condensation of fluid in the pore. These results could prove useful in the characterization of these porous structures.

L'objectif de ce travail de thèse est l'élaboration d'une photodiode organique (OPD) destinée à être intégrée dans un biocapteur. Ce travail s'inscrit dans le cadre plus général de l'étude et de l'amélioration de composants organiques impliqués dans des microsystèmes de détection visant à surveiller la pollution de l'eau. Le besoin d'évaluation et de suivi de la qualité de l'eau suscite un grand intérêt pour des systèmes de détection portables de polluants ayant une réponse rapide et de faible coût. Le principe de la mesure repose sur la détection des variations de fluorescence de micro-algues en présence de substances toxiques. Excitées grâce à une diode électroluminescente (LED) bleue, les algues vont émettre un signal de fluorescence dont l'intensité, modifiée en présence de polluant (Diuron), est détectée par l'OPD optimisée. Le signal de fluorescence à détecter étant très faible, l'OPD idéale doit avoir un faible courant d'obscurité et une grande sensibilité. Cela passe par un choix judicieux des matériaux semi-conducteurs organiques (OSC) entrant dans l'élaboration de la couche active du composant. Pour accompagner le choix des matériaux, il est intéressant d'explorer leurs propriétés physico-chimiques tout en essayant de rationaliser les mécanismes mis en jeu au sein de ces matériaux lorsqu'ils sont utilisés dans l'élaboration d'OPD (phénomènes d'absorption de photons, mécanismes de transport de charges, et pertes associées aux recombinaisons de charges). Cette thèse s'articule autour de deux axes. Le premier axe consiste en une étude théorique qui vise à comprendre et à maitriser l'échange des charges à l'échelle nanométrique par des caractérisations optiques et des calculs de chimie quantique basés sur des méthodes DFT et TD-DFT. L'étude sur un système modèle (le P3HT) a permis d'établir un protocole de calcul très prometteur pour l'étude des propriétés de matériau d'intérêt, en particulier le PTB7. Le second axe est un volet à caractère expérimental. L'élaboration, la caractérisation et l'optimisation d'OPD à base de PTB7 : PC60BM a permis de concevoir un biocapteur algal apte à détecter le Diuron à des concentrations de l'ordre du nanomolaire. / The aim of this thesis is to develop an organic photodiode (OPD) designed to be integrated into a biosensor. It is part of the broader framework of studying and improving organic components involved into devices devoted to water pollution monitoring. The need for such portable, fast-response, low-cost microsystems is of great interest. The measurement is based on the fluorescence detection of micro-algae under toxic substances exposure. The excited algae, under a blue light emitting diode (LED), will emit a fluorescence signal whose intensity, modified because of pollutant exposure (Diuron), is detected by the OPD. Since the fluorescence signal is very weak, the ideal OPD must have a low dark current and a high sensitivity. To achieve this performance, a judicious choice of organic semiconductor materials (OSC) used for the OPD is required. In addition, it is interesting to investigate their physico-chemical properties by rationalizing the mechanisms involved in the active layer (photon absorption phenomena, charge transport mechanisms, and losses associated with charge recombinations). This thesis is based on two axes. The first one consists in a theoretical study of the charge exchanges at a nanoscale. This have been done by both optical characterizations and quantum chemistry calculations based on DFT and TD-DFT methods. Calculations were performed on a model system (P3HT) thus providing the basis for a very promising computational protocol for studying the properties of materials of interest, for instance PTB7. The second axis concerns the experimental study of the OPD based on PTB7:PC60BM. We have developed, characterized and optimized an OPD guarantying the detection of algal fluorescence without and with Diuron at about nanomolar concentrations.

I performed first principles studies of the site occupancy and magnetic properties of zinc-tin-substituted strontium hexaferrite by using density functional theory. In this study, I determined the site preference of zinc and tin atoms when they are restricted to occupy the same sublattice in strontium-hexaferrite. I found that Zn and Sn atoms prefer to replace Fe ions at 2a sublattice under this restriction and caused the saturation magnetization to decrease.