This work focuses on an examination of the high-accuracy extrapoloated ab initio thermochemistry (HEAT) protocol of determining molecular atomization energies. The HEAT protocol does not utilize experimental data or empirical scaling effects. The accuracy of the approach is tested via comparison to ATcT data, and all molecules fall within 1 kcal/mol of accepted values. There are several important points to note about this treatment: namely, that we have used atomic natural orbital (ANO) basis sets for the calculation of the zero point energy and that we have made determinations for larger molecules than previously done with HEAT. The molecules in this paper were chosen to provide benchmark numbers for the homodesmotic reaction heirarchy as described by Wheeler et al.[3] The relative accuracy of the approach is considered, as well as a discussion of possible remaining sources of error. / text

Submitted by Nelson Bretanha (physikosmos@gmail.com) on 2016-01-01T12:55:20Z No. of bitstreams: 1 Métodos Semi-Empíricos (Princípios Básicos e Aplicações).pdf: 4755970 bytes, checksum: 0e2d74ff6ffd8de112da824ec714d84e (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-01-05T18:04:11Z (GMT) No. of bitstreams: 1 bretanhaneto_ne_me_rcla.pdf: 4755970 bytes, checksum: 0e2d74ff6ffd8de112da824ec714d84e (MD5) / Made available in DSpace on 2016-01-05T18:04:11Z (GMT). No. of bitstreams: 1 bretanhaneto_ne_me_rcla.pdf: 4755970 bytes, checksum: 0e2d74ff6ffd8de112da824ec714d84e (MD5) Previous issue date: 2015-12-18 / Neste trabalho investigamos os efeitos decorrentes da presença de heteroátomos numa folha de “supercoroneno” (molécula C58H18 utilizada como uma primeira aproximação para o grafeno). Mais especificamente, utilizando método semi-empírico PM6, implementado no pacote computacional MOPAC2012®, estudamos as diferentes curvas de energia (calor de formação). As curvas estudadas foram obtidas pela passagem de um átomo de carbono sobre uma folha de supercoroneno na qual existe um heteroátomo (foram utilizadas três diferentes estruturas: C57H18Si, C57H18Ge e C57H18Sn). Nesse contexto, estudamos também o efeito destes heteroátomos sobre a densidade eletrônica e os orbitais HOMO e LUMO das diferentes estruturas. / In this work we investigate the effects of the presence of heteroatoms on a “supercoronene” sheet (C58H18 molecule used as a molecular model for graphene). Specifically, we used the semiempirical method PM6 as implemented in MOPAC2012® software to study several (formation) energy curves. The energy curves were obtained by positioning a carbon atom over a “supercoronene” sheet in which there is a heteroatom (this was done for three different structures: C57H18Si, C57H18Ge and C57H18Sn). In this context, the effect of these heteroatoms on the electronic density distributions, as well as their effect on HOMO and LUMO orbitals were also investigated.

Produktion av nya energetiska material är dyrt. Målet med detta arbete är att utveckla en metod som uppskattar Chapman-Jouget detonationstrycket och detonationshastigheten hos nya CHNO-sprängämnen. En sådan metod möjliggör valet att bara syntetisera och testa de mest lovande kandidaterna som nya energetiska material, därmed undviks resursslösande arbete. Den här metoden använder sig av density functional theory (DFT) och den elektrostatiska potentialen till att uppskatta bildningsentalpier och kristalldensiteter. Beräkningarna gjordes på traditionella sprängämnen och de beräknade detonationstrycken och detonatioshastigheterna visade bra överensstämmelse med experimentell data. Detonationstrycken hamnade inom ±10% och detonatioshastigheterna inom ±5% av experimentell data. / Producing new energetic materials is expensive. This work aims to develop a method of estimating the Chapman-Jouget detonation pressure and the detonation velocity of potential new CHNO explosives. This would allow choosing the most promising candidates for synthesis and testing thus avoiding wasting resources. This method utilizes density functional theory (DFT) and the electrostatic potential to estimate heats of formation and crystal densities. The calculations were performed on traditionally used explosives and the calculated detonation pressures and detonation velocities showed good accordance with experimental data. The calculated detonation pressures fell within ±10% and the detonation velocities within ±5% of experimental data.

Advances in computing capabilities have facilitated the application of quantum mechanical methods to increasingly larger and more complex chemical systems, including weakly interacting and biologically relevant species. One such ab initio-based composite methodology, the correlation consistent composite approach (ccCA), has been shown to be reliable for the prediction of enthalpies of formation and reaction energies of main group species in the gas phase to within 1 kcal mol-1, on average, of well-established experiment, without dependence on experimental parameterization or empirical corrections. In this collection of work, ccCA has been utilized to determine the proton affinities of deoxyribonucleosides within an ONIOM framework (ONIOM-ccCA) and to predict accurate enthalpies of formation for organophosphorus compounds. Despite the complexity of these systems, ccCA is shown to result in enthalpies of formation to within ~2 kcal mol-1 of experiment and predict reliable reaction energies for systems with little to no experimental data. New applications for the ccCA method have also been introduced, expanding the utility of ccCA to solvated systems and complexes with significant noncovalent interactions. By incorporating the SMD solvation model into the ccCA formulation, the Solv-ccCA method is able to predict the pKa values of nitrogen systems to within 0.7 pKa unit (less than 1.0 kcal mol-1), overall. A hydrogen bonding constant has also been developed for use with weakly interacting dimers and small cluster compounds, resulting in ccCA interaction energies for water clusters and dimers of the S66 set to within 1.0 kcal mol-1 of well-established theoretical values.

The work is focused on the obtaining thermochemical properties of the linear polynitramines to predict their detonation properties. The basic thermochemical parameters are enthalpies ?f H° (298,g) in the gas and solid phase as well. The values of the enthalpy in the gas phase were obtained at a theoretical level by quantum chemical DFT calculations using both an isodesmic reactions and direct thermochemical G-Gaussian recipes. Conversion to the enthalpy in the solid phase ?f H° (298,s) was carried out using sublimation enthalpies ?s H° (298,g) obtained on the empirical level. The results were mutually compared and correlated with the structure of the linear polynitramines.

La synthèse de composés énergétiques fortement azotés, à partir des réactifs et des processusissus de la chimie des hydrazines, a permis une nouvelle approche de composés de type HEDM(High Energy Density Materials) pour la propulsion spatiale. En effet, la formation de diazote(N−−−N) à partir d’une liaison N−−N libère de grandes quantités d’énergie, et davantage depuis uneliaison N−N. L’amination de la diméthylhydrazine dissymétrique (UDMH) a conduit à un sel de2,2-diméthyltriazanium, possédant trois atomes d’azote reliés uniquement par des liaisons sigma.L’anion inorganique de départ a ensuite été échangé avec des anions énergétiques à plus haut tauxd’azote — 5-aminotétrazolate, 5-nitrotétrazolate, 5,5’-azobistétrazolate, azoture, nitroformiate etdinitroamidure. Pour des raisons de sécurité, l’échange d’ions impliquant l’anion azoture a étéréalisé par électrodialyse et la sensibilité à l’impact ainsi qu’à la friction de ces sels a été évaluéeselon les normes en vigueur. L’analyse des composés les plus riches en azote par calorimétrie decombustion a permis de déterminer leurs enthalpies de formation de manière fiable. Ces dernièresont ensuite été modélisées par des méthodes de chimie quantique et comparées aux procéduresreportées dans la littérature, dont les aspects théoriques ont été discutés. La procédure conduisantaux enthalpies de formation en meilleure adéquation avec les valeurs expérimentales a étéidentifiée ; sa précision excède d’ailleurs celle de résultats récents d’équipes reconnues. Ainsi, lesmoyens mis en place dans le cadre de cette thèse permettront de progresser plus efficacementdans cette nouvelle thématique au laboratoire. / High nitrogen content energetic compounds, envisioned as a first step towards High EnergyDensity Materials (HEDM) for space propulsion, were prepared from hydrazine derivatives. Indeed,the formation of nitrogen gas (N−−−N) from an N−−N bond yields a lot of energy and even morefrom an N−N bond. Hence, an amination reaction on unsymmetrical dimethylhydrazine (UDMH)yielded a 2,2-dimethyltriazanium salt, containing three consecutive single-bonded nitrogen atoms.The initial inorganic anion was then exchanged with the following nitrogen-rich anions in order toyield energetic salts: 5-aminotetrazolate, 5-nitrotetrazolate, 5,5’-azobistetrazolate, azide, nitroformateand dinitramide. For safety reasons, the ion metathesis of the azide salt was conductedby electrodialysis and the sensitivities of all compounds towards both impact and friction wereevaluated in accordance with standard procedures. Reliable heats of formation of the compoundswith the highest nitrogen content were obtained by oxygen bomb calorimetry. These values werethen computed with quantum mechanical methods and compared with known procedures reportedin the literature, whose theoretical backgrounds have been discussed. Consequently, theprocedure resulting in the best match between calculated and experimental heats of formation wasidentified. The precision of the method used herein exceeds that of recent results from renownedresearch groups in this field. Thus, the various techniques introduced during the course of thiswork will enable our laboratory to progress more efficiently in this area of research.

Ce travail est consacré au développement de composés polyazotés de la famille des tétrazènes, pour des applications dans le domaine de la propulsion spatiale. Compte tenu de la forte toxicité des hydrazines utilisées actuellement dans les systèmes à biergols stockables, il devient absolument nécessaire de les remplacer par de nouveaux ergols verts, performants au niveau propulsion, et ne présentant pas d'impact significatif sur la santé humaine et l'environnement. Aujourd'hui, le candidat idéal pour remplacer les hydrazines spatiales n'a pas été identifié, mais un premier candidat a été proposé par le CNES en raison de ses performances théoriques et d'une toxicité moindre, il s'agit du 1,1,4,4-tétraméthyl-2-tétrazène (TMTZ). Dans cette thèse, une caractérisation complète de ce composé a été effectuée, afin de valider son intérêt en tant qu'ergol. Une étude cinétique et thermodynamique a permis de proposer un procédé de synthèse du TMTZ propre, performant en continu, intégrant les phases de synthèse, d'extraction et de purification. Pour aller plus loin dans cette démarche, de nouvelles cibles polyazotées ont été identifiées, dans le but d'atteindre des performances plus importantes en élaborant des structures tétrazènes plus riches en atomes d'azote que le TMTZ. Les différentes voies de synthèse de ces tétrazènes densifiés sont présentées, ainsi que la réactivité de leurs précurseurs potentiels. En appui de ces recherches, des outils théoriques et expérimentaux de prédiction et de détermination des performances énergétiques des composés polyazotés sont présentés / This work aims at the development of polynitrogen-based compounds of the tetrazene family for space propulsion applications. Due to the high toxicity of hydrazines used currently in stockable bipropellant systems, there is a need to replace them by new green propellants with high propulsion performance and low impact towards human health and the environment.So far, the ideal candidate to replace space-use hydrazines has not been identified. However, the French Space Agency (CNES) proposed a first candidate, namely, 1,1,4,4-tetramethyl-2-tetrazene (TMTZ), which has a high theoretical performance and exhibits lower toxicity. In this work the latter compound was fully characterized in order to validate its interest as a propellant. Kinetic and thermodynamic studies allowed to propose a continuous synthesis process for pure TMTZ, which involves a synthesis, an extraction and a purification steps. In this context, new polynitrogen-based target molecules were identified in order to achieve higher performances than TMTZ and tetrazene derivatives with a higher nitrogen content were synthesized. Herein, the different synthesis pathways of these tetrazene derivatives with higher density as well as the reactivity of their potential building blocks are presented. To complete the above research, theoretical and experimental methods for the prediction and measurement of the energetic performance of the polynitrogen-based compounds are also presented

The main goal of the presented thesis is a theoretical study of heat of formation for high-nitrogen energetic materials. A modification of the classical approach to the isodesmic reactions is realized with the intent that molecules on both sides of the corresponding equation have not only the same number of atoms but also approximately the same size and skeletal similarity. This approach is designated as a method "Alternative Isodesmic Reaction (AIR method)". At its base, using the DFT B3LYP / cc-pVTZ and B3PW91 / cc-pVTZ, for the high nitrogen heterocycles, which are selected from the group of triazoles, triazines, tetrazines, the enthalpy of formation values the gaseous phase f H°(298,g), were obtained whose values are close to the published f H°(298,g). Their application in the calculation of the relevant characteristics of these heterocycles detonation gave real values.