Teses / dissertações sobre o tema "Dynamique moléculaire ab initio; DFT"
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Ducher, Manoj. "Fractionnement isotopique du zinc à l'équilibre par calcul ab initio". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066318/document.
Texto completo da fonteIsotopic compositions are used to study the biogeochemical cycle of Zn, which is greatly impacted by anthropic activities. However, the interpretation of the measurements performed on natural or synthetic samples requires the knowledge of Zn isotope properties in equilibrium conditions (as reference) and the understanding of the mechanisms that are at the origin of the isotopic composition variations. In this work, we determined by performing quantum calculations, equilibrium Zn isotope fractionation constants in various phases including solids and liquids. We highlighted the crystal-chemical parameters controlling the isotopic properties : Zn interatomic force constant, Zn-first neighbours bond lengths and the electronic charge on atoms involved in the bonding. We carried out a methodological development in order to calculate isotopic properties in liquid phases from molecular dynamics trajectories at a reduced computational cost. We showed through the modelling of aqueous Zn that a reasonable description of van der Waals forces using a non-local exchange correlation functional is required to stabilise the experimentally observed hexaaquo zinc complex over other complexes at room temperature. This work provides a consistent database of equilibrium Zn isotope fractionation constants for experimental works
Grisolía, Maricarmen. "Étude de structure électronique et de processus dynamiques de systèmes chimiques complexes". Toulouse 3, 2010. http://thesesups.ups-tlse.fr/1702/.
Texto completo da fonteThis work is about the theoretical study of several systems and some of their dynamical processes. First, we have applied different electronic structure calculation methods to the structural study of glass systems made of gallium, lanthanum and sulfur, whose physical properties have been observed to be improved by cesium chloride doping. We have confirmed that previously obtained experimental results are insufficient to explain this changes and that these studies must be completed by additional experiments. Particularly, our calculations have shown that pertinent informations could be obtained by studying these glasses by vibrational spectroscopy. Second, we have studied the compound Ag2V4O11 (SVO) by means of the Density Functional Theory (DFT). This compound is largely used as electrode material for lithium batteries. We have obtained results partly clarifying a controversy relative to the crystal structure of SVO, for which three different structures have been reported. We have then made an ab initio molecular dynamics study of the mobility of metallic ions in this system. Our results give useful informations for the understanding of the complex mechanism of lithium insertion on SVO. Lastly, we have studied a case of a system which is not under the Born-Oppenheimer approximation. We have simulated the tunneling process of a quantum particle evolving in a metastable potential well, and we have estimated its tunneling time, by means of an original semiclassical molecular dynamics method. The use of these ab initio calculation methods for the study of these three different cases has allowed us to evaluate their capacity to elucidate electronic structure problems and to describe physical-chemical phenomena existing in complex systems
Rey, Jérôme. "Mechanisms and kinetics of alkenes isomerization and cracking in chabazite zeolite quantified by constrained ab initio molecular dynamics". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEN049.
Texto completo da fonteHydrocracking and hydroisomerization catalysts are bifunctional, with a hydro-dehydrogenation function and an acidic function, typically an acid zeolite, to isomerize and crack alkenes. With advanced ab initio molecular dynamics approach, and explicit simulation of the effects of temperature (300 – 500 K), we investigate the mechanisms of isomerization and cracking reactions of C7 alkenes within the chabazite zeolite in order to provide reliable rate constants and explain the observed products distribution. By blue moon sampling, we established for the first time, the free energy profiles for the isomerization of C7 alkenes in zeolites, with carbenium ions as intermediates (and protonated cyclopropane (PCP) as transition states), connecting di- to tri-branched, and mono- to di-branched alkene isomers (Sections III and IV). We demonstrate that the dynamic effects with the correct sampling of rotational conformers play an important role to quantify the stability of the key intermediates and transition states. These effects could not be captured by previous static DFT simulations. The much lower barriers for type A isomerization mechanisms are thus recovered, and assigned to a loose transition state, while the transition state of type B isomerization is tighter, due to the formation of an edge PCP. The study of cracking reactions (Section V) with the same methods, unravel the role of secondary cations. For the first time, we identify the structures of transition states involved in the β-scission mechanisms. From this analysis, we deduce the ab initio- rate constants that could be used in future kinetic modeling to predict activity and selectivity of the catalyst
Ducher, Manoj. "Fractionnement isotopique du zinc à l'équilibre par calcul ab initio". Electronic Thesis or Diss., Paris 6, 2017. http://www.theses.fr/2017PA066318.
Texto completo da fonteIsotopic compositions are used to study the biogeochemical cycle of Zn, which is greatly impacted by anthropic activities. However, the interpretation of the measurements performed on natural or synthetic samples requires the knowledge of Zn isotope properties in equilibrium conditions (as reference) and the understanding of the mechanisms that are at the origin of the isotopic composition variations. In this work, we determined by performing quantum calculations, equilibrium Zn isotope fractionation constants in various phases including solids and liquids. We highlighted the crystal-chemical parameters controlling the isotopic properties : Zn interatomic force constant, Zn-first neighbours bond lengths and the electronic charge on atoms involved in the bonding. We carried out a methodological development in order to calculate isotopic properties in liquid phases from molecular dynamics trajectories at a reduced computational cost. We showed through the modelling of aqueous Zn that a reasonable description of van der Waals forces using a non-local exchange correlation functional is required to stabilise the experimentally observed hexaaquo zinc complex over other complexes at room temperature. This work provides a consistent database of equilibrium Zn isotope fractionation constants for experimental works
Le, Roux Sébastien. "Étude par dynamique moléculaire ab-initio des verres de chalcogénures GeS2 et (M2S)0.33(GeS2)0.66 M=Na, Ag". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2008. http://tel.archives-ouvertes.fr/tel-00688343.
Texto completo da fonteLe, Roux Sébastien. "Étude par dynamique moléculaire ab-initio des verres de chalcogénures GeS2 et (M2S)0. 33(GeS2)0. 66 M=Na,Ag". Montpellier 2, 2008. http://www.theses.fr/2008MON20106.
Texto completo da fonteAb-initio molecular dynamics simulations are used to study GeS2 and (M2 S)0. 33 (GeS2 )0. 66 M=Na,Ag chalcogenide glasses. A new theoretical method which uses ring statistics is proposed in order to analyse the connectivity of amorphous materials. The cooling rate effect on the physical properties of the GeS2 glasses is analysed. The medium and short range order analysis reveals the existence of a maximum cooling rate above which the structure of the material is too similar to the one of the liquid. This is confirmed by the ring statistics analysis which also highlights major differences between the connectivity of the liquid and the glassy GeS2 structures. Finally the existence of extended charged regions in the glassy GeS2 matrix is confirmed even for the lowest cooling rates. The conditions needed to observe the diffusion of the sodium atoms in the glassy (Na2 S)0. 33 (GeS2 )0. 66 matrix are studied. When the diffusion process occurs the displacement of the sodium atoms seems to become cooperative. Parametrisation attempts are done in order to model (Ag2 S)0. 33 (GeS2 )0. 66 and GeS2 chalcogenide glasses using the SIESTA code
Richard, Pauline. "Exploration ab initio du diagramme de phases de l'or à haute pression et haute température". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF040.
Texto completo da fonteThis thesis is dedicated to exploring the phase diagram of gold under high pressure and high temperature. Calculating the free energy is fundamental for comparing the relative stability of phases under specific thermodynamic conditions. However, this quantity explicitly depends on the partition function, making it challenging to calculate in atomistic simulations. It is often decomposed into cold and thermal contributions. Among these contributions, the lattice dynamics, or phonons, play a crucial role. The temperatures explored induce indeed anharmonic effects, necessitating the use of expensive ab initio methods, based on density functional theory (DFT) which are the most appropriate method to account for these effects that existing empirical potentials cannot reproduce. Coupled with thermodynamic integration, it is the reference method for calculating free energy. However, this method remains very time-consuming and is thus prohibitive to explore the whole phase diagram of gold. Alternative methods exist, such as the quasi-harmonic approximation, but its validity at high temperature is difficult to assess. The goal of this thesis is to propose a method that maintains DFT accuracy while reducing computation time. To achieve this, an accelerated sampling procedure using machine learning is employed. This procedure allows for the training of surrogate potentials, which are then used a posteriori to extract the Gibbs free energies of the considered structures via a non-equilibrium thermodynamic integration calculation. The results obtained have been validated by comparison with those from the temperature-dependent effective potential. In the first part, this approach was applied to construct the phase diagram of solid gold from 0 to 1 TPa and up to 10,000 K. It shows the stabilization of a body-centered cubic (bcc) phase at high temperatures, around 200 GPa. An explanation for the cubic face-centered (fcc)-bcc transition before melting was proposed, based on the effects of interatomic force constants. Furthermore, the stability domains of the fcc and hexagonal close-packed (hcp) phases predicted by this study are in good agreement with most recent experimental results. In the second part, this procedure was extended to calculate the melting curve of gold
Halbert, Stéphanie. "Étude du comportement dynamique de systèmes catalytiques greffés sur silice". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2013. http://tel.archives-ouvertes.fr/tel-01005016.
Texto completo da fonteCaussé, Maélie. "Étude de quelques propriétés de superhydrures à haute pression et à haute température". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF041.
Texto completo da fonteOver the past ten years, a new chemistry of hydrogen with metals has been observed under high pressures. Very hydrogen-rich compounds, called superhydrides, form in the 100 GPa range. Remarkable properties of these compounds have been highlighted, such as BCS superconductivity at very high critical temperatures, like LaH₁₀ with a hydrogen cage sublattice and superconductivity at -23 ° C. A current question is whether such compounds can be stable at ambient pressure, and the path of ternary hydrides is currently being explored. Firstly, using ab initio molecular dynamics calculations, we have revealed a new property of LaH₁₀ : superionicity, which indicates very rapid diffusion of hydride ions. This property should exist for other superhydrides. Secondly, we have searched for ternary hydrides in the Y-Fe-H system. By compressing, under high hydrogen pressure in a diamond anvil press, the Laves phase compound YFe₂, well known for its hydrogen storage capacity at ambient pressure, we discovered two interstitial hydrides, YFe₂H₆ and YFe₂H₇. We also demonstrated a limit to hydrogen incorporation in this type of compound. These two compounds are not stable at ambient pressure. Finally, using laser heating, we synthesized the ternary hydride Y₃Fe₄H₂₀, which was brought back metastable at ambient pressure. The structure and properties of this superhydride were characterized by single-crystal X-ray diffraction and ab initio calculations. An unprecedented structure for a hydride is highlighted with [FeH₈] anionic entities linked to each other and forming cages around yttrium cations. This compound is metallic and this structure could serve as a model to find a ternary hydride superconductor stable at ambient pressure
Cheik, Njifon Ibrahim. "Modélisation des modifications structurales, électroniques et thermodynamiques induites par les défauts ponctuels dans les oxydes mixtes à base d'actinides (U,Pu)O2". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0356/document.
Texto completo da fonte(U,Pu)O2 (commonly called MOX) is currently used as nuclear fuel in pressurized water reactors with a Pu content of around 10 wt.%, and is envisaged as the reference fuel in Generation IV sodium fast reactors (SFR) with a Pu content of around 25 wt.%. Under operation, (U,Pu)O2 is submitted to fission reactions which generate a large quantity and variety of point defects, as well as fission products. By migrating, point defects and gaseous fission products can aggregate into nano-voids, dislocations and fission gas bubbles, which lead to the modification of the fuel microstructure. Therefore, a better description of the fuel behaviour at the atomic scale, and especially of the elementary mechanisms involved in the diffusion of point defects and fission products, is necessary to refine the models used in the fuel performance codes used to simulate the behaviour of fuels at the macroscopic scale. We use electronic structure calculations based on the DFT+U method combined with the occupation matrix control scheme (OMC) to investigate (U,Pu)O2 properties for various Pu contents. Static energy minimizations and ab initio molecular dynamics were used. We have first determined bulk structural, electronic and thermodynamics properties of (U,Pu)O2. We then studied the stability of point defects in (U,Pu)O2 and (U,Ce)O2, as well as the structural and electronic modifications induced by these point defects, in (U,Pu)O2 and the common experimental surrogate (U,Ce)O2. Finally, the fission gas (Kr and Xe) and helium (He) trapping and solubility in (U,Pu)O2 matrix are investigated
Rasim, Karsten. "Conductivité protonique et structures locales par simulations ab initio d'oxydes utilisés comme électrolyte dans les piles à combustible". Phd thesis, Université de Nantes, 2011. http://tel.archives-ouvertes.fr/tel-00983483.
Texto completo da fonteDel, Fré Samuel. "Études théoriques de la photodésorption d'analogues de glaces moléculaires interstellaires : application au monoxyde de carbone". Electronic Thesis or Diss., Université de Lille (2022-....), 2024. http://www.theses.fr/2024ULILR039.
Texto completo da fonteUnusual amounts of gas-phase molecules are detected in the cold regions (around 10 K) of the interstellar medium (ISM), primarily attributed to the non-thermal desorption of molecules from ices deposited on dust grains. In particular, vacuum ultraviolet (VUV) photon-induced desorption (photodesorption) is considered a major desorption pathway in photon-dominated regions of the ISM. Experimental investigations have revealed that in pure carbon monoxide (CO) ices, a ubiquitous species in the ISM, VUV photodesorption can follow an indirect mechanism of desorption induced by electronic transitions (DIET) for photons with energy between 7 and 10 eV. Nevertheless, the understanding of the underlying molecular mechanisms remains a topic of scientific debate. In this astrochemical context, we present a combined theoretical study using ab initio molecular dynamics (AIMD) based on density functional theory (DFT) and machine learning potentials (PML) constructed with artificial neural networks (ANN) to study the final part of the DIET mechanism in amorphous CO ices. Here, a highly vibrationally excited CO molecule (v = 40) at the center of an aggregate initially composed of 50 CO molecules, optimized and then thermalized at 15 K, triggers the indirect desorption of surface molecules. Our theoretical results reveal that the desorption process consists of three fundamental steps, beginning with a mutual attraction between the vibrationally excited molecule and one or two neighboring molecules, activated by CO bond stretching and facilitated by the steric effect of surrounding molecules. This is followed by a sequence of energy transfers initiated by a collision, resulting in the desorption of vibrationally cold CO molecules in 88% of the AIMD trajectories. Additionally, the theoretical distributions of the internal and translational energy of desorbed molecules remarkably match experimental results, supporting the crucial role of vibrational relaxation in the desorption process. Finally, the first PML constructed from AIMD simulations accurately fit the multidimensional potential energy surface of the system, allowing efficient prediction of aggregate energies and atomic forces. Classical molecular dynamics simulations using these potentials are over 1800 times faster than those based on AIMD while offering precision comparable to DFT
Failali, Abdelmounaim. "Molecular modeling of organic phases after plutonium extraction". Electronic Thesis or Diss., Université de Lille (2018-2021), 2021. http://www.theses.fr/2021LILUR002.
Texto completo da fonteThe nuclear fuel after its dwell time in reactor still bears a substantial amount of recoverable U and Pu. The recovery and purification of these actinides is achieved using a hydro-metallurgical process known as PUREX (Plutonium Uranium Recovering by EXtraction). Based on Liquid-Liquid extraction techniques, this process requires the use of a specific molecule to extract Pu and U, the tri-n-butylphosphate TBP. N,N-dialkylamides (monoamides) are regarded as an alternative family of extractants to TBP, as they are well-known for their strong extraction ability of Pu(IV) and U(VI) elements. In addition to this, they show some interesting features, such as, the strong dependence of the extraction properties (distribution coefficient and selectivity) on the ligands structure as well as chemical conditions. In order to propose the best extracting molecule design for future fuel reprocessing plants, it is crucial to understand the relationship between the structure and the extraction ability. However, the radioactivity of these elements combined with their chemical complexity make the study of these phases experimentally a real challenge. Hence, molecular modeling appears to be the golden solution for getting new insights on this issue.In the first part of this thesis, a relativistic density functional theory study was performed to investigate the influence of the monoamides alkyl chain nature on the relative stability of Pu(IV) complexes. It was possible to reach a better understanding of the strong influence of amide structure on plutonium extraction. For both investigated amide-plutonium-nitrate complexes (inner and outer-sphere complexes), it was found that the introduction of a bulky alkyl group on the carbonyl side has a major impact on the complexation energy. The impact of the polarity of the solution was also investigated and found to be significant.In the second part, within the aim of studying more realistic systems, i.e systems containing long alkyl chains monoamides, heavy elements and other counter ions, and to go beyond the static picture of QM/DFT optimized geometries with molecular dynamics simulations, we have developed a consistent polarizable FF model for the solvent molecules (alkanes, monoamides) based solely on quantum chemical calculations. The chosen ab initio parameterization approach as well as the final force field are presented. Then, the results of molecular dynamics simulations were compared to available experimental macroscopic thermodynamics and structural properties, and show an excellent agreement, making the predictions of properties of pure monoamides reliable. Finally, preliminary MD simulations results for monoamides-dodecane mixtures (DEHiBA/dodecane and DEHBA/dodecane) are presented
Cheik, Njifon Ibrahim. "Modélisation des modifications structurales, électroniques et thermodynamiques induites par les défauts ponctuels dans les oxydes mixtes à base d'actinides (U,Pu)O2". Electronic Thesis or Diss., Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0356.
Texto completo da fonte(U,Pu)O2 (commonly called MOX) is currently used as nuclear fuel in pressurized water reactors with a Pu content of around 10 wt.%, and is envisaged as the reference fuel in Generation IV sodium fast reactors (SFR) with a Pu content of around 25 wt.%. Under operation, (U,Pu)O2 is submitted to fission reactions which generate a large quantity and variety of point defects, as well as fission products. By migrating, point defects and gaseous fission products can aggregate into nano-voids, dislocations and fission gas bubbles, which lead to the modification of the fuel microstructure. Therefore, a better description of the fuel behaviour at the atomic scale, and especially of the elementary mechanisms involved in the diffusion of point defects and fission products, is necessary to refine the models used in the fuel performance codes used to simulate the behaviour of fuels at the macroscopic scale. We use electronic structure calculations based on the DFT+U method combined with the occupation matrix control scheme (OMC) to investigate (U,Pu)O2 properties for various Pu contents. Static energy minimizations and ab initio molecular dynamics were used. We have first determined bulk structural, electronic and thermodynamics properties of (U,Pu)O2. We then studied the stability of point defects in (U,Pu)O2 and (U,Ce)O2, as well as the structural and electronic modifications induced by these point defects, in (U,Pu)O2 and the common experimental surrogate (U,Ce)O2. Finally, the fission gas (Kr and Xe) and helium (He) trapping and solubility in (U,Pu)O2 matrix are investigated
Pezzotti, Simone. "DFT-MD simulations and theoretical SFG spectroscopy to characterize H-Bonded networks at aqueous interfaces : from hydrophobic to hydrophilic environments Structural definition of the BIL and DL: a new universal methodology to rationalize non-linear χ(2)(ω) SFG signals at charged interfaces, including χ(3)(ω) contributions What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy 2D H-Bond Network as the Topmost Skin to the Air-Water Interface Combining ab-initio and classical molecular dynamics simulations to unravel the structure of the 2D-HB-network at the air-water interface 2D-HB-Network at the air-water interface: A structural and dynamical characterization by means of ab initio and classical molecular dynamics simulations Spectroscopic BIL-SFG Invariance Hides the Chaotropic Effect of Protons at the Air-Water Interface Molecular hydrophobicity at a macroscopically hydrophilic surface Graph theory for automatic structural recognition in molecular dynamics simulations DFT-MD of the (110)-Co3O4 cobalt oxide semiconductor in contact with liquid water, preliminary chemical and physical insights into the electrochemical environment". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLE008.
Texto completo da fonteImproving our knowledge on water H-Bonded networks formed in the special environment offered by an interface is pivotal for our understanding of many natural phenomena and technological applications. To reveal the interfacial water arrangement, techniques able to provide detailed microscopic information selectively for the interfacial layer are required. In the present thesis work, we have hence investigated aqueous interfaces at the molecular level, by coupling theoretical modeling from DFT-MD simulations with SFG & THz-IR spectroscopies. By developing new investigation protocols/tools, coupling DFT-MD simulations and SFG spectroscopy, in particular for the more complex rationalization of charged interfaces, we have provided a global comprehension of the effect of various interfacial conditions (hydrophilicity, pH, ionic strength) on the HB-Network formed in the interfacial layer (BIL), on its spectroscopic signatures and on its impact on physico-chemical properties. We have shown for the first time that, in sufficiently hydrophobic conditions, BIL interfacial water creates special 2-Dimensional HB-Networks, experimentally revealed by one specific THz-IR marker band. Such 2D-network dictates HBs and orientational dynamics of interfacial water, surface potential, surface acidity, water surface tension and thermodynamics of hydration of hydrophobic solutes. Such "horizontal ordering” of water at hydrophobic interfaces is found opposite to the “vertical ordering” of water at hydrophilic interfaces, while coexistence of the two orders leads to disordered interfacial water in intermediate hydrophilic/hydrophobic conditions. Both DFT-MD and SFG further revealed how ions & pH conditions alter these BIL-water orders
Rio, Jérémy. "Modélisation à l'échelle atomique de Cycloparaphénylènes avec les techniques ab initio". Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4078/document.
Texto completo da fonteThe work in this thesis concerns the study at the atomic scale of Cycloparaphenylene ([n]CPP) molecules and their complexes and derivatives, using ab initio modeling methods (DFT/LDA). I initially look at the stability of these molecular rings when functionalized by halogens, and the structural changes induced. The important notion of curvature energy is raised to find new synthesis routes. The encapsulation of C60 fullerene inside [10]CPPs is a very important part of this work and more particularly the interaction between the azafullerene dimer (C59N)2 and two [10]CPPs. This allowed us to look at supramolecular interactions and the alignment of two [10]CPPs on this dimer both theoretically and experimentally, through collaboration with research teams in Germany and Greece. The possibility of templated alignment of [10]CPPs leads to a study on the functionalization of these molecules with the aim of connecting them together with various connectors, for example with aromatic species, polymers or metals to form a new family of pseudo-nanotubes composed of multiply inter-linked [10]CPPs. Depending on the connections used, the conduction properties of the 'pseudo-nanotubes' can vary from wide-gap semiconductors to metallic structures. I also show in this manuscript, that [n]CPPs and carbon nanotubes can interact to form structures where the ring is encapsulated inside or around the carbon nanotube. In this context, the study of the rotation of cycloparaphenylene demonstrate a very low frictional force and thus predict ultra-rapid CPP rotation
Raynaud, Christophe. "Dynamique moléculaire ab initio en base locale : principes et applications". Phd thesis, Université Paul Sabatier - Toulouse III, 2005. http://tel.archives-ouvertes.fr/tel-00079109.
Texto completo da fonteRichter, Falk. "Etude théorique de l'isomérisation cis-trans de HO-NO par les méthodes ab-initio". Marne-la-Vallée, 2004. http://www.theses.fr/2004MARN0222.
Texto completo da fonteLasoroski, Aurélie. "Etude de complexes de gadolinium d’intérêt pour l’IRM : simulations ab-initio et propriétés magnétiques". Paris 6, 2013. http://www.theses.fr/2013PA066216.
Texto completo da fonteCurrently MRI exams use contrast agents to enhance contrast imaging and so diagnostics. A contrast agent is most of the time a gadolinium complex in which a chelate ligand is used to avoid Gd release, thus preventing toxic ion to spread in patient’s body. In this thesis we studied magnetic properties of gadolinium complexes that affect the relaxation of a water molecule coordinated to Gd, which is the source of contrast imaging. We focused on the commercial contrast agent ProHance, and some derivatives. The first step was to compute ab initio molecular dynamics of the different systems and analyse them. Then we calculated using quantum chemistry hyperfine interaction and Zero-Field Splitting. The analysis of hyperfine tensors was achieved for each system, and average terms were estimated. The origin of tensors’ fast fluctuations in ProHance system was identified thanks to geometrical collectives variables decomposition. ZFS was decomposed into two contributions: static and transient. We can now set up from ab initio all the necessary ingredients for modeling the electronic relaxation time and then the water coordinated molecule proton relaxation for each of the studied systems
Despré, Victor. "Dynamique électronique à l'échelle attoseconde et femtoseconde en physique moléculaire : une approche ab-initio". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10142/document.
Texto completo da fonteThe advent of attosecond physics has brought new experimental and theoretical challenges. Indeed, the observation of dynamic processes occurring at the intrinsic time scale of charge motion at atomic scale, allows to consider new processes for which the role of correlations and non-adiabatic couplings become primordial. The work presented in this manuscript falls in the context of the study of complex molecules subject to a short light pulse. For such time (femtosecond / attosecond) and energy scales (IR / XUV), the main approximations that permit the study of electronic systems are no longer appropriate. In this thesis, we present the simulations realized for the theoretical study of molecules in such conditions. We studied the correlated charge migration dynamics in several molecules like the benzene, different polycyclic aromatic hydrocarbons and molecules of biological interest such as phenylalanine. This kind of dynamics has never been observed experimentally. Hence, a particular attention was paid to the feasibility of an experiment in the case of the benzene molecule. The non-adiabatic relaxations of the naphthalene molecule subjected to a XUV pulse were also studied. Finally, dynamics occurring at the optical cycle time scale experienced by a group of medium-sized molecules subject to an IR pulse, were discussed. These simulations were used to interpret pump-probe experiments made by members of our team
Krebs, Emmanuel. "Modélisation moléculaire ab initio des effets de morphologie en catalyse par les sulfures". Paris 6, 2008. http://www.theses.fr/2008PA066174.
Texto completo da fonteBlaineau, Sébastien. "Propriétés physico-chimiques des verres chalcogénures GeS2 et xNa2S-(1-x)GeS2 : une étude par dynamique moléculaire "ab initio"". Montpellier 2, 2005. http://www.theses.fr/2005MON20172.
Texto completo da fonteFoulie, Colette. "Dynamique et toxicité de protéines avec une haute homologie de séquences : approche par dynamique moléculaire et calculs ab-initio". Phd thesis, Université de Bourgogne, 2008. http://tel.archives-ouvertes.fr/tel-00367817.
Texto completo da fonteAnglade, Pierre-Matthieu. "Etude du comportement mécanique du tantale sous pression par dynamique moléculaire". Université de Marne-la-Vallée, 2004. http://www.theses.fr/2004MARN0214.
Texto completo da fonteMichel, Carine. "Études théoriques de la réactivité chimique". Grenoble 1, 2007. http://www.theses.fr/2007GRE10075.
Texto completo da fonteStakes and difficulties of theoretical studies of chemical reactivity are highlighted through various chemical systems: phosphatase biomimetic complexe, tandem acetalisation/cyclisation reaction, Pauson-Khand reaction. This last study even lead us to propose a new electropsray source calibration. To go beyong the traditionnal methods limits, we used the metadynamics method, which can sample the phase space of chemical systems and overcome rare events problem. Associated with ab initia Born-Oppenheimer dynamics, we have demonstrated that metadynamics can be efficient to study organometallics reactions. Furthermore, we have initiated a novel strategy to evaluate directly entropy thanks to metadynamics. The first results are promising, as weIl as in organometallics reactivity than in water dimer dissociation
Li, Zhi. "Ab initio study of the supercritical state of iron". Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEN003.
Texto completo da fonteIron as a building block material of the Earth naturally received significant attention. Considerable efforts have been made to determine its thermodynamic and thermophysical properties up to the Earth’s inner core’s conditions. However, its physical properties in the low-density regime are less explored, and notably the position of the liquid-vapor equilibrium line and of the critical point are lacking. The missing information inhibits developing a complete equation of state that covers the released state after shock waves, and thus hinders the characterization of large planetary impacts.The present study aims at closing the knowledge gap on the liquid-vapor equilibrium dome of iron. For this we exploit molecular dynamics and Monte Carlo methods where the energy and the forces are estimated by the density functional theory. We then employ statistical and thermodynamics methods to construct the position of the critical point, build the liquid-vapor dome, and characterize the physical properties of the fluid iron.First we determine the position of the critical point from ab initio molecular dynamics simulations along several isotherms. The simulation results provide the position of the liquid spinodal above 3000 K, and the gas spinodal close to the critical point. We bracket the position of the critical point in the 9000-9350 K temperature range, and 1.85-2.40 g/cm3,density range, corresponding to 4-7 kbars pressure range. Additionally, we characterize the structure and the transport properties of the fluid iron over a wide density and temperature range, with a particular focus on the supercritical state.Then we compute two Hugoniot lines starting with two realistic initial conditions. By comparing the entropy values calculated along these Hugoniot lines to that at the boiling point, we find that the pressure required to reach the onset vaporization is significantly lower than previous estimates. It suggests that previous hydrodynamic simulations underestimate the iron vapor production, and that the core of Theia underwent partial vaporization during the giant impact. Similarly, we find that a large fraction of the planetesimals falling on Earth during the late veneer must have had their cores undergoing partial vaporization. The readily achieved partialcore vaporization would enhance the iron-silicates equilibration, which helps explain geochemical observations.At last, we determine the liquid-vapor equilibrium line of iron. For this, we have extended and implemented the Gibbs ensemble Monte Carlo method coupled with the finite-temperature density functional theory. The first benchmark test to sodium shows a good agreement with available experimental results. We then apply this technique to iron and calculate its liquid density in equilibrium with the vapor phase. We also show the importance of magnetism diminishes as approaching the critical point
Guihery, Nathalie. "Recherche et conception d'édifices moléculaires bistables : études ab initio et développement d'Hamiltoniens magnétiques". Toulouse 3, 1995. http://www.theses.fr/1995TOU30292.
Texto completo da fonteLucas, Guillaume. "Etude théorique à l'échelle nanométrique du carbure de silicium sous irradiation : modélisation classique et ab initio". Poitiers, 2006. http://www.theses.fr/2006POIT2313.
Texto completo da fonteChaker, Ziyad. "Etude par dynamique moléculaire ab initio des propriétés magnétiques, électroniques et structurales des matériaux lamellaires hybrides organiques-inorganiques". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE016/document.
Texto completo da fonteAb-initio molecular dynamics (AIMD) refers to a set of state-of-the-art computational methods combining molecular dynamics with density functional theory. It is the basis of what could be called a «Virtual laboratory approach». In this work, we use the Car-Parrinello Molecular Dynamics (CPMD) scheme for investigating the properties of Copper Hydroxide Acetate system, a typical organic-inorganic hybrid material. We determine the corresponding atomic structure as well as several of its chemical and magnetic properties. Recent experimental achievements provide accurate XRD measurements enabling the study of magneto-structural properties of Cu2 (OH)3 (CH3 COO). compound. The pressure-induced magnetic transition, observed experimentally (at 1,2 GPa) in this material has been successfully reproduced (close to 2 GPa), thereby, highlighting the role of structural optimizations in theoretical treatments of such materials. Our aim is to elucidate the complex interplay between structural properties, interfacial inte r facial chemistry and magnetic behaviors of various nanoscale structured materials both at the local (atomic) and bulk (crystal) levels. We focus on copper hydroxide-based hybrid materials spanning through different organic components (such as fluorene mono- or di-phosphonic molecules) considered prototypical and very promising in the field of hybrid multifunctional materials
Martinez, Michael. "Simulation ab initio de modules d'intérêt biologique : modes de vibrations pour la spectroscopie infrarouge". Paris 6, 2006. http://www.theses.fr/2006PA066620.
Texto completo da fonteYu, Lantao. "Optimisation par inclusion, alliage et dopage des matériaux thermoélectriques d'intérêt - application des méthodes ab initio et de dynamique moléculaire". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS056/document.
Texto completo da fonteThermoelectricity is considered a promising source of energy since it is able to directly convert heat into electricity. This makes it possible to recover dissipated heat without causing pollution. However, large-scale applicative options are still under restriction because of the dim thermoelectric conversion yield. Therefore, numerous research works are dedicated to improving thermoelectric performance of different materials, which is characterized by the dimensionless figure of merit ZT. A favorable ZT includes simultaneously a satisfying Seebeck coefficient, a high electrical conductivity and a low thermal conductivity. To seek a suitable material with a better thermoelectric performance is the objective of our analyses. With doping technics, different elements can be added into semi-conductors within different concentrations. The charge density could be thus modified in order to change thermoelectric properties. Due to hurdles related to materials synthesis, numerical simulations based on different methods, such as density functional theory (DFT), molecular dynamics (MD), are then implemented to estimate the most promising improvement approach. During this thesis, thermoelectric properties of several materials are investigated for applications in different situations, i.e. CsSnI₃ as a potential candidate with its high electronic conductivity, ZnO as a transparent thermoelectric material, Bi₂Te₃ as a traditional material with further improvements and cellulose as future organic semi-conductor. As DFT concerns only properties of electrons (Seebeck coefficient, electric conductivity, thermal conductivity due to electrons), lattice thermal conductivity is not included herein. Therefore, DFT with finite displacement and MD are used as a complementary method to establish thermal conductivity due to phonons. In this way, this thesis is divided into two parts. In the first part, theoretical backgrounds of DFT are introduced starting with Schrödinger equation. Results of classical DFT simulations are presented afterwards. By using atomic positions from experimental measurements, we launched crystal structure relaxation to ensure that every atom in the system is at its equilibrium position. Electronic band structures are also calculated to validate calculation configurations (cutoff energy, convergence conditions, etc.). A full mapping of Eigenvalues in reciprocal space is realized and thermoelectric properties are calculated by solving Boltzmann transport equations. In the second part, basic theories of phonons are mentioned, followed by introductions of DFT with finite displacements and MD methods. We implemented MD simulations to study the influence of aluminum doping on lattice thermal conductivity for ZnO. We also used DFT with finite displacements method to study lattice thermal conductivity variation of Bi₂Te₃₋ₓSeₓ alloy
Ganster, Patrick. "Modélisation de verres intervenant dans le conditionnement des déchets radioactifs par dynamiques moléculaires classique et ab initio". Montpellier 2, 2004. http://www.theses.fr/2004MON20124.
Texto completo da fonteAyoub, Aaeid. "Études ab initio et dynamique moléculaire des propriétés structurales et thermodynamiques de la calcite et la witherite sous hautes pressions". Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10074/document.
Texto completo da fonteIn this thesis we use two efficient methods: the density functional theory (DFT) based on pseudopotential method, and molecular dynamics to understand and analyze the different properties of calcite and witherite. In particular we focused on the mechanical and thermodynamic properties of these two rocks. The computed quantities (elastic constants, bulk modulus, specific heat, ...) compare well with the experimental or constitute reliable predictions for future work on these rocks. The effect of high hydrostatic pressure shows, through a calculation of total energy and enthalpy of formation, transition to new phases, which are structurally different and, consequently, with new properties. In addition, the calculated X-ray spectra show again the good agreement of our results with existing experimental measurements, confirming the validity of the method and the potential used. Moreover, new potential parameters developed in this thesis for the classical molecular dynamics will enable future studies in this area
Mortazavi, Amiri Narjes Beigom. "Relations entre motifs structuraux et dynamique de réseau dans les cristaux mixtes Cu-Zn-Sn-Se : études premiers principes". Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0333/document.
Texto completo da fonteThe works addresses vibrational properties of novel semiconductors, specifically the Cu2ZnSnSe4 and Cu2ZnSnS4 compounds of the kesterite structure, which, in the domain of photovoltaics, become competitive with leading materials of chalcopyrite type, notably Cu(In,Ga)Se2. The anticipated immediate practical interest of such study is that the vibration spectra are likely to make possible a distinction between different structural phases, possible for a given composition. The vibration modes are accessed by using a first-principle theory approach. The manuscript is divided into five chapters, with the following contents: (1) A brief introduction into the work principle and the problematics of photovoltaics, specifically of the solar cells based on multinary semiconductors; the chapter closes by the description of the phase diagram of the Cu-Zn-Sn-Se system. (2) An overview of the density functional theory (DFT) and of the technics of numerical simulations using the SIESTA code. (3) The vibrational properties of Cu2ZnSnSe4 in its two phases, kesterite and stannite, as studied by first-principles method, with a detailed comparison being done along with a thorough mode-by-mode analysis. (4) Vibrational properties of a secondary phase Cu2SnSe3, which often competes with the Cu2ZnSnSe4 phase in the process of sample growth. (5) Calculation of phonons in the Cu2ZnSnS4 structure containing intrinsic defects (vacances; anti sites), with the objective of estimating vibrational contributions to entropy and the correction of the composition - temperature phase diagram in this multi nary system. The general conclusion summarises the results which are published in 5 articles
Louit, Guillaume. "Développement de sondes fluorescentes du radical hydroxyle : caractérisation et modélisation de la réactivité de molécules dérivées de la coumarine avec HO". Paris 11, 2005. http://www.theses.fr/2005PA112170.
Texto completo da fonteThe hydroxyl radical is involved in a wide range of different fields, from oxidative stress to atmospheric chemistry. In addition to the study of oxidative damage in biological media, the hydroxyl radical detection allows to perform a dosimetry when it is produced by ionising radiation. The aims of this work have been double:- to improve the detection of the hydroxyl radical by the design of new probes- to improve knowledge on the reactive pathways in which the hydroxyl radical is involved. We have studied the coumarin molecule, as well as 6 derivatives that we have synthesised, as fluorescent probes of the hydroxyl radical. Firstly, fluorescence spectroscopy and HPLC chromatography have allowed the evaluation of the sensibility and selectivity of detection of the probes. Consequently to this study, two applications have been developed, concerning the determination of rate constants by competition kinetics and bidimentional dosimetry. Secondly, we have studied the reactivity of the hydroxyl radical through the regioselectivity of its addition on the aromatic cycle. This problem was addressed by the combined use of experimental methods such as time resolved kinetics and HPLC along with interpretation from classical and ab initio modelisation
Wang, Yu. "Ab initio calculation of H interactions with defects in fcc metals : crack tip dislocations and vacancies". Thesis, Toulouse, INPT, 2014. http://www.theses.fr/2014INPT0125/document.
Texto completo da fonteIn many technological applications of structured metallic alloys, hydrogen embrittlement (HE) is a major concern as it can penetrate in most metals, degrade their properties and lead to premature failures. Despite numerous efforts in the past decades during which many microscopic mechanisms were proposed, a clear understanding of H embrittlement mechanisms has not been achieved yet. Since HE processes occur on an atomic-scale, the exact mechanisms leading to HE are not easily identified experimentally. One possible improvement would be to use atomic-scale simulations to try to capture details of deformation and fracture processes at the atomic level, enabling the investigation of relevant microscopic mechanism. In such context, the goal of this PhD work is to understand and quantify H interactions with defects like vacancies, dislocations and cracks in fcc metals through multi-scale modeling. The study is organized in four main parts. In the first part, we employed first principle calculations (based on density functional theory) to describe H interaction with a vacancy in Nickel. More specifically, the segregation energies of multiple H atoms in a single and di-vacancies were computed. Two characteristic energies were found which clarify the experimental peaks observed in Thermal Desorption Spectra in the literature. The equilibrium concentrations of H-vacancy clusters was then evaluated, under conditions relevant to HE and stress corrosion cracking (SCC) of Ni based alloys (nuclear industry),by Monte Carlo simulations and a thermodynamic model developed from our DFT data. In the second part, we quantified the trapping effect of vacancies on H diffusion in Nickel. With DFT computed jump barriers, related to H trapping and detrapping in vacancies, we employed accelerated Kinetic Monte Carlo (KMC) simulations to evaluate the H diffusion coefficient as a function of vacancy concentration and temperature. In the third part, we studied the diffusion of H-vacancy clusters in Ni, based on the combination of DFT and a statistical method. DFT calculations of vacancy jump barriers were performed for clusters containing from one to six H inside the vacancy. With these computed barriers and previous calculated concentrations of H-vacancy clusters, a simple stochastic model similar to the KMC procedure was developed to estimate the diffusion coefficient of H-vacancy clusters as a function of H concentration and temperature. In the last part, we studied the interaction of hydrogen with a blunted crack tip in Aluminum by combined EAM (semi-empirical interatomic potential) and DFT calculations. Embedded atom method (EAM) potential simulations were performed to evaluate the H effect on dislocation emission from a blunted crack tip under mixed mode loading. This phenomenon can be understood by the H induced change of the unstable stacking fault energy (γus ) in Rice’s model. Therefore, DFT and EAM calculations of γus were performed including the effects of H and of the mixed mode loads. It is shown that the effect of the load perpendicular to the glide plane is very strong, contrary to the effect of sub-surface H, which is negligible
Gauthier, Laurent. "Exemple d'étude structurale et dynamique en phase liquide et liquide surfondu : quinoléine et lépidine". Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10151.
Texto completo da fonteBaroni, Axelle. "Etude structurale de B2O3 à l'aide de simulations de dynamique moléculaire incluant des potentiels polarisables". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066265/document.
Texto completo da fonteBoron trioxyde, B2O3, is the archetype of network-forming system with trigonal basic structural units under ambient conditions. In the glass under ambient conditions, it has been established that these triangles are packed in superstructural units called boroxol rings. Using molecular dynamics simulations including polarisable potentials we studied structural transformations of B2O3 in glassy, liquid and cristalline phases. We followed the boron coordination change as a function of pressure and the disapperance of boroxol rings at high pressure and high temperature. Results obtained using our potentials are in good agreement with experimental data: neutron diffraction and X-ray diffraction. They belong to best potentials in literature to describe correctly B2O3 structure
Diarra, Cheick Oumar. "Modélisation par dynamique moléculaire ab initio du transport des excitons et du transport thermique dans les semiconducteurs organiques pour la collecte d'énergie". Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAD013.
Texto completo da fonteThe exciton plays a central role in the functioning of organic solar cells (OSCs). Understanding its dynamics in organic semiconductors is essential, particularly to optimize the diffusion length, a key property for the performance of planar heterojunctions, which are considered as a potentially more stable alternative to bulk heterojunctions (BHJ) in certain contexts. In the first part of this thesis, we developed a robust and versatile methodological approach to evaluate the exciton diffusion length in organic semiconductors. This method, based on AIMD-ROKS, was successfully validated for the P3HT polymer. It was also applied to the NFA O-IDTBR acceptor, revealing promising diffusion lengths, though still insufficient for planar heterojunctions. The second part of the thesis explores heat transfer in organic semiconductors, a crucial element for the performance of thermoelectric devices. These studies focused on P3HT, a material used in thermoelectricity. First, the thermal conductivity within P3HT chains was studied, revealing the influence of polymer chain length. Then, heat transfers between these chains were also examined
Moog, Mathieu. "Carbon dioxide at extreme conditions : liquid(s), crystals, glasses and their transformation from ab initio topological methods". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS263.
Texto completo da fonteAlthough carbon dioxide is well known for its impact on the atmosphere, it is also an important constituent of the mantle of earth. As such, it is implicated in a number of geological events, notably in earthquakes and volcanism. In this thesis we aim at understanding the behavior of carbon dioxide in the lower mantle, where it is likely formed through reactions between carbonates and silicon dioxide. Indeed, the properties of carbon dioxide, and most notably its polymerization mechanisms may impact the reactivity of the mantle and therefore impact the chemical properties occurring within it. In this work we use state of the art topological descriptors and ab initio simulation methods to study the polymerization mechanisms that occurs under the extreme conditions corresponding to the lower mantle of Earth. We notably show the existence of four distinctive fluids that coexist at those conditions, including: a reactive molecular fluid with the regular formation of dimers allowing the exchange of oxygen between carbon dioxide molecules; a very reactive polymeric fluid which forms a complex network in perpetual evolution; and a very sluggish liquid, very similar to an amorphous solid ; and the standard molecular liquid with long range interactions between carbon dioxide molecules. All of those different fluids occur within the experimental conditions of the lower mantle and therefore may have potential implications for its reactivity and transport properties. The reactive molecular liquid, for example, implies that carbon dioxide will take an important part in the chemical reactions of the mantle
Abadie, Sacha. "Vibrational excitation of molecules in the gas phase or embedded in matrices by ab initio molecular dynamics". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLE057/document.
Texto completo da fonteIn the thesis we have studied two prototypical systems in both condensed and gas phase,to follow and quantify the vibrational energy flow through normal modes after vibrational excitation.For the condensed phase, we considered a host Formic Acid immersedin an argon matrix, while for the gas phase we have studied the N-Methyl Acetamid... Cl.. Ar cluster. After the preparation of initial conditions using a semi-classical Wigner sampling, several DFT-MD trajectories have been performed to analyse the Intra/Inter vibrational energy relaxation. Two theoretical methods have been used to follow the evolution with time of the vibrational quantum numbers: a new method based on the study of vibrational density of states (VDOS)compared with a more traditional method based on the study of the amplitude of a specificmotion of the molecule (i.e. distance or angle). Both methods reveal similar results.In the condensed phase, the quantum yield of the trans/cis isomerisation process of theFormic Acid molecule has been compared to the experimental data. We have shown that thevibrational excitation of two combination modes involves in some cases the isomerisation ofthe Formic Acid molecule. This initial vibrational excitation of the Formic Acid has also animpact on the surrounding matrix: the energy initially contained into the FA is redistributedto the matrix leading to the deformation and the melting (solid-liquid transition) of theargon matrix.In the gas phase, we have shown that vibrational excitation of the N-H stretching motion ofthe (Cl...NMA) involves the systematic loss of the argon atom. Finally, the two models have shown that in both condensed or gas phase environment, after the vibrational excitation (n=1) of a normal modeat t=0 of the dynamics, this normal mode comes back in its ground state (n=0)
Hernandez, Jean-Alexis. "Ab initio modeling of dense water ices at extreme conditions of pressure and temperature". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN028/document.
Texto completo da fonteIn this thesis we study the stability and the properties of pure and NaCl-bearing dense water ices at high pressure (between 5 and 300 GPa) and high temperature (between 300 and 2000 K). To reach these conditions that correspond to the interiors of ocean exoplanets, we employ a theoretical approach based on ab initio molecular dynamics simulations. We show that a detailed analysis of the hydrogen bond dynamics allows to distinguish all the different ice phases presenting a body-centered cubic sub-lattice of oxygen atoms. In particular, we present the first ab initio description of the plastic phase of water ice. We also reveal the multiple transitions that occur in the superionic domain. Next, we show that ice VII' can incorporate up to 5.9 wt% NaCl in its structure at 1600 K. The inclusion of Na+ and Cl- ions enhances the orientation disorder of the water molecules in comparison to the pure ice. From 2.5 wt% NaCl, superionic conduction expands over the entire pressure range studied, and the hydrogen symmetrisation is shifted towards higher pressures. Last, we describe the <110> and <111> screw dislocation core structures of ice X at 80 GPa. This constitutes a first step towards the construction rheological laws for high-pressure cubic ices
Lucas, Guillaume. "Etude théorique à l'échelle nanométrique du carbure de silicium sousirradiation : modélisation classique et ab initio". Phd thesis, Université de Poitiers, 2006. http://tel.archives-ouvertes.fr/tel-00127786.
Texto completo da fontetypes de potentiels ont été utilisés : le potentiel de Tersoff, qui donne des résultats peu satisfaisants, et un nouveau potentiel développé dans le cadre de cette thèse. Ce potentiel permet une meilleure modélisation du SiC sous irradiation que la plupart des potentiels empiriques disponibles pour le SiC. Il est basé sur une fonction de type EDIP, initialement développée pour décrire les défauts dans le silicium, que nous avons généralisé au SiC. Pour l'approche ab initio, la faisabilité des calculs a été validée et des énergies moyennes de 19 eV pour C et 38 eV pour Si ont été déterminées, proches des valeurs empiriques utilisées dans la communauté scientifique. Les résultats obtenus avec le nouveau potentiel EDIP sont globalement en accord avec ces valeurs. Enfin, les processus élémentaires impliqués dans la guérison du cristal ont été étudiés en calculant la stabilité relative des paires de Frenkel formées et en déterminant des mécanismes de recombinaisons possibles par la méthode Nudged Elastic Band.
Naseem-Khan, Sehr. "Development of a polarizable ab initio force field : From separability of intermolecular interactions to condensed phase properties". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS564.
Texto completo da fonteThanks to the recent progresses of computer sciences de-multiplying the available computational resources, the possibility of using sophisticated polarizable force fields such as SIBFA becomes a reality. Indeed, the SIBFA intermolecular potential and its gradients are now implemented in the Tinker-HP package. The original calibration of SIBFA was based on the RVS method, an energy decomposition analysis only available at the Hartree–Fock level of theory. Therefore, the goals of this work are double : i) choosing a new energy decomposition analysis reference scheme in order to upgrade the SIBFA parameters at the correlated level of theory ; ii) performing molecular dynamics. The first part of this thesis is dedicated to the study of the separability of the ab initio intermolecular interaction energy predicted by both variational and perturbational Energy Decomposition Analysis methods. We have made improvements for the induction energy term within the SAPT(DFT) method, and we have proposed a new charge transfer definition. The second part of this thesis is dedicated to the development of the SIBFA polarizable water model and to our definition of a strategy to compute condensed phase properties. The ab initio study of the separability of the total SAPT(DFT) intermolecular interaction energy has led the SIBFA potential to achieve both full separability of its components and high accuracy at the post Hartree-Fock level. This thesis marks a turning-point for the SIBFA potential, finalizing its global bottom-up strategy going from gas phase ab initio computations towards molecular dynamics simulations and accurate condensed phase properties predictions
Martin, Nicolas. "Composite C/C à matrice nanochargée en alumine et en nitrure d'aluminium". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0237/document.
Texto completo da fonteA hydrothermal-like process to introduce nano-structured alumina and aluminum nitride in carbon/carbon (C/C) composites is developped. Starting from dissolved reactants in an aqueous media,nanoparticules with various morphology are synthesised. The understanding and control of the processis completed in two steps. In the former the study on simplewafer type substrat allows to identifythe key parameters of the process. During the latter a scaling up of the process is done to allow thesynthesis in situ of C/C composites. The microstructural and some mechanical characterization ofthe four ranges of material produced is achieved.In addition several carbon|alumina and carbon|aluminumnitride are simulated using an ab initiomolecular dynamic approach. The methdology to generate the models consists in sumulating theliquid quench of a high temperature amorphous carbon inbetween fixed ceramic surface, then torelease the constrains. Depending on the system, different organisations of the nano-carbons withinthe surfaces are identified : when the graphene sheets are pependicular to the surface, the modelshows an important number of strong bonds and the simulation traction behavior is good, whereaswhen they are parallel to the surface it leads to weak interface and mechanical behavior.Finally HRMET charasterization of some of the materials produced allows to identify experimentalinterfaces alike to those obtained during themolecular dynamic simulations
Geneste, Grégory. "Mécanismes élémentaires de la croissance oxyde sur oxyde : étude ab initio et semi-empirique de MgO/MgO(001)". Toulouse 3, 2003. http://www.theses.fr/2003TOU30156.
Texto completo da fontePéoux, Gérald. "Étude théorique par la méthode des paquets d'ondes quantiques de la photodissociation de la molécule HBr et des collisions réactives indirectes du type A + BC -> AB + C". Lille 1, 1997. http://www.theses.fr/1997LIL10209.
Texto completo da fonteAwali, Slim. "Dynamique de relaxation électronique d’un atome métallique déposé sur agrégat d’argon". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112013/document.
Texto completo da fonteThis thesis is a study on the interaction between electronically excited atomic states and a non-reactive environment. We have theoretically and experimentally studied situations where a metal atom (Ba or K) is placed in a finite size environment (argon cluster). The presence of the medium affects the electronic levels of the atom. On the other side, the excitation of the atom induces a relaxation dynamics of the electronic energy through the deformation of the cluster. The experimental part of this work focuses on two aspects : the spectroscopy and the dynamics. In both cases a first laser electronically excites the metal atom and the second ionizes the excited system. The observable is the photoelectron spectrum recorded after photoionization and possibly information on the photoion which are also produced. This pump/probe technique, with also two lasers, provide the ultrafast dynamic when the lasers pulses used are of ultrashort (60 fs ). The use of nanosecond lasers leads to resonance spectroscopic measurement, unresolved temporally, which give information on the position of the energy levels of the studied system. From a theoretical point-of-view, the excited states of M-Ar_n were calculated at the ab initio level, using large core pseudo-potential to limit the active electrons of the metal to valence electrons. The study of alkali metals (potassium) is especially well adapted to this method since only one electron is active. The ab-initio calculation and a Monte-Carlo simulation where coupled to optimize the geometry of the KAr_n (n = 1-10) cluster when K is in the ground state of the neutral and the ion, or excited in the 4p or 5s state. Calculations were also conducted in collaboration with B. Gervais (CIMAP, Caen) on KAr_n clusters having several tens of argon atoms. Absorption spectra were also calculated. From an experimental point-of-view, we were able to characterize the excited states of potassium and barium perturbed by the clusters. In both cases a binding ∏-state, and an anti-binding ∑ -state were observed. In the case of potassium, we observered that the excitation on the ∑ -state leads to the ejection of the metal within 1-2 ps while for barium, the excited state relaxes mainly on the ∏-state within 6 ps and does not followed by an ejection. The interpretation of these results uses the structures and potential calculated. A similar study was conducted on the DABCO molecule deposited argon cluster. Instead of K and Ba, the first excited state of this molecule is a diffuse isotropic state, which gives a specific relaxation to the photoinduced dynamics
Jeanvoine, Yannick. "Modélisation ab initio des silicates, aluminosilicates et silicoaluminophosphates. Etude structurale et dynamique des sites acides de Bronsted dans HSSZ-13 et Hsapo-34". Nancy 1, 1998. http://docnum.univ-lorraine.fr/public/SCD_T_1998_0251_JEANVOINE.pdf.
Texto completo da fonteMaliyov, Ivan. "Irradiation ionique des matériaux : dynamique des excitations électroniques en temps réel". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS434.
Texto completo da fonteIonic irradiation damage in condensed matter is central to many technological applications: materials in nuclear plants of course, but also electronics and solar panels in space that are subjected to the cosmic irradiation, living matter treated by radiotherapy to eliminate tumors, etc. For all these subjects, an accurate knowledge of the interaction between the irradiating projectile and the target is crucial. The interaction between the irradiating ion and the target material can be described by a stopping power, defined as the energy transfer from projectile to material per penetration distance. The most important ionic energy loss channels in the irradiation process are the electronic excitations. Therefore, the electronic stopping power is the central quantity in this field. With the advent of time-dependent density-functional theory (TDDFT), it is nowadays possible to provide a complete and realistic quantum-mechanical description of the phenomenon.In this thesis, we have developed a fully ab initio real-time TDDFT (RT-TDDFT) approach in the localized Gaussian basis. This implementation has several appealing advantages, such as the cheap account of core electrons, the ease of using the modern hybrid functionals, the flexibility of the basis set and overall low computational cost. With our tool, we explored the bulk limit, the validity of the projectile impact parameter averaging to obtain the experimental random electronic stopping power. We have proven the importance of core electron excitations in the ionic irradiations. A great care wasalso taken about the Gaussian basis set convergence: the extrapolation of the stopping power based on standard basis sets and the basis set generation scheme were proposed.Finally, we have computed the random electronic stopping power in lithium and aluminum targets for three types of projectiles: protons, antiprotons, and alpha-particles. We have compared our results directly to the experiment as well as to the empirical code SRIM, which is a widely-used database of stopping powers and a de facto standard for experimentalists. The agreement with SRIM is good when the SRIM database contains enough experimental points, whereas we show that the SRIM extrapolation can be hazardous when the underlying experimental data points are too few. Concerning the antiproton irradiation, our RT-TDDFT calculations show that the antiproton stopping power is lower than the proton one, which is in agreement with the general experimental observation (the so-called Barks effect). This effect is out of reach of simpler theories, such as the linear response approximation