A caracterização no estado sólido de insumos farmacêuticos constitui uma parte muito importante no entendimento de suas propriedades físicas, químicas e farmacológicas. A partir da análise estrutural por difração de raios X em monocristal, pode-se identificar a conformação no estado sólido do fármaco, assim como sua densidade eletrônica. Estes estudos podem ser complementados com dados provenientes da Modelagem Molecular, que compreende um número de ferramentas e métodos computacionais e teóricos que têm como objetivos compreender e prever o comportamento de sistemas reais. Nesse contexto, visando compreender melhor as propriedades de estado sólido apresentadas pelo fármaco anti-filariose dietilcarbamazina (DEC), foi obtido um novo sal, o maleato de dietilcarbamazina (DEC maleato), cujas propriedades foram comparadas com as das estruturas já reportadas, DEC citrato e DEC pura. A DEC maleato foi caracterizada por difração de raios X em monocristal, espectroscopias Raman e Infravermelho e análise térmica. A DEC maleato cristaliza no grupo espacial triclínico PI com dois confôrmeros da molécula de DEC na unidade assimétrica, ambos exibindo caudas etílicas na conformação syn em relação ao anel piperazina, diferentemente do que ocorre na DEC citrato e na DEC pura, nas quais esses fragmentos moleculares apresentam uma conformação anti. A principal interação intermolecular entre o fármaco e o ácido maleico é do tipo N-H•••O, que caracteriza a formação do sal e, consequentemente, do par iônico (DEC)+(maleato)-. Além disso, uma rede complexa de interações intermoleculares não-clássicas do tipo C-H•••O estão presentes entre as moléculas de DEC, DEC-maleato e maleato-maleato, levando a um empacotamento cristalino na forma de um sanduíche, onde os confôrmeros da DEC acomodam-se em colunas intercaladas por bicamadas de íons maleato. Não foram observadas transições de fase estruturais em função da temperatura entre 100 K e temperatura ambiente. No entanto, devido à variação conformacional observada entre as moléculas de DEC, cálculos quânticos foram realizados na fase gasosa, otimizando as conformações moleculares tanto da molécula de DEC neutra quanto da carregada a fim de determinar as características de sua estrutura eletrônica utilizando o método da Teoria do Funcional de Densidade, com o funcional híbrido B3LYP e o conjunto de função de base 6-31++G. Através dos cálculos teóricos foram obtidas quatro novas conformações, uma para DEC neutra e três da carregada, para as quais analisou-se as energias de conformação, os espectros vibracionais simulados e por fim os mapas de potencial eletrostático e os orbitais de fronteira. / The solid state characterization of active pharmaceutical ingredients (API) constitutes an important part in understanding their physical, chemical and pharmacological properties. From the structural analysis by single crystal X-ray diffraction, the API conformation in the solid form, as well as its electronic density, can be identified. These studies can be supplemented with data from the Molecular Modeling, which includes a number of theoretical and computational tools used to understand and to predict the behavior in real systems. In this context, aiming to better comprehend the solid state properties exhibited by the anti-filarial drug diethylcarbamazine (DEC), a new salt was obtained, the diethylcarbamazine maleate (DEC maleate), and its properties were compared with the ones of the reported structures, DEC citrate and pure DEC. The DEC maleate was characterized by single crystal X-ray diffraction, infrared and Raman spectroscopy and thermal analysis. DEC maleate was found to crystallize in the triclinic space group PI with two very similar conformers of the DEC molecule in the asymmetric unit, both exhibiting the ethylic chains in conformation syn in relation to the piperazine ring, unlike what happens to DEC citrate and pure DEC, where these chains are anti related. The main intermolecular interaction between the API and the maleic acid is of the type NH•••O, characterizing the salt formation, and thus, the ionic pair (DEC)+(maleate)-. Moreover, a complex network of no-classical intermolecular interactions of the type CH•••O occur between DEC-DEC, DEC-maleate, and maleate-maleate molecules, leading to a sandwich like crystal packing, where DEC conformers are accommodated in columns intercalated by maleates bilayers. No phase transitions were observed for the molecule structure in function of temperature between 100 K and room temperature. However, due conformational variations observed among DEC molecules of the three structures, quantum calculations were performed in the gas phase, optimizing the molecular conformations of both, the neutral and the charged DEC molecules to determine the characteristics of the electronic structure using the method of Density Functional Theory with the B3LYP hybrid functional and basis set 6-31++G. new conformations it were found, for which geometrical characteristics, conformation energies, vibrational spectra simulation and finally the electrostatic potential maps and the frontier orbitals, were analyzed.

In non-relativistic quantum mechanics, stationary states of molecules and atoms are described by eigenvectors of the Hamiltonian operator. For one-electron systems, such as the hydrogen atom, the solution of the eigenvalue problem (Schro ̈dinger’s equation) is straightforward, and the results show excellent agreement with experiment. Despite this success, the multi electron problem corresponding to virtually every system of interest in chemistry has resisted attempts at exact solution. Perhaps the most popular method for obtaining approximate, yet very accurate results for the ground states of molecules is the coupled cluster approximation. Coupled cluster methods move beyond the simple, average field Hartree-Fock approximation by including the effects of excited configurations generated in a size consistent manner. In this paper, the coupled cluster approximation is developed from first principles. Diagrammatic methods are introduced which permit the rapid calculation of matrix elements appearing in the coupled cluster equations, along with a systematic approach for unambiguously determining all necessary diagrams. A simple error bound is obtained for the ground state energy by considering the coupled cluster equations as entries in the first column of a matrix whose eigenvalues are the exact eigenvalues of the Hamiltonian. In addition, a strategy is considered for treating the error in the ground state energy perturbatively.

<p>This thesis is intended to be a ground for the implementing of solid mechanics calculations of an expander axle in an existing CAD programme. The main parameters to be calculated are: effective stress, stress components in axial and radial direction, shear stress as well as maximum force and fatigue analysis. In order to achieve the above mentioned goal, calculations were made by hand. At the end of any of the chapters, a diagram on the input/output data and the equations needed for performing the calculations was drawn.</p>

<p>Using field theoretical methods models of strongly correlated electrons have been investigated. Application to electronic structure calculations has been made.</p><p>In this thesis an attempt is made to build a bridge between first-principle band structure calculations and a theory of systems with strongly correlated electrons, by making use of perturbation theory from the atomic limit. Analyzing the total non-relativistic Hamiltonian leads to the basic model of strongly correlated systems, the Hubbard-Anderson model. In this thesis these basic models have been tested. Conclusions on delocalization and many-body aspects have been extracted from the solutions. Specifically for the lanthanides a separation of the f-system into two subsystems has resolved the discrepancy between calculated equilibrium volumes and experimental ones. The calculations are done within the Hubbard-I approximation, where it is possible to define renormalized fermion operators. The calculation is a true many-body calculation.</p><p>Using perturbation theory a set of self consistent equations has been formulated, and solved, for praseodymium metal using the periodical Anderson model. The solution shows a self consistent decrease of the Hubbard U, and delocalization of the f-shell, when crucial parameters of the model are changed. The most salient feature of the models for strongly correlated electrons is the transfer of spectral weight from one energy region to another by adjusting pressure or other external parameters. The effects come from kinematic interactions that are important for strongly correlated systems.</p><p>Investigations of the degenerate Hubbard model applied to the metal to insulator transition has also been made. When the degeneracy is considered, the transition to the metallic state occurs at smaller Coulomb energies. </p><p>The validity of the Fermi liquid description for strongly correlated electrons has also been studied. The results show that the general behavior of the Fermi liquid state is quite robust.</p>

We study the effects of vibrations in the Pd₃ system using first-principles pseudopotential calculations. We find that upon disordering from the DO₂₂ phase, the decreases by 0.07kB. We explain our results in terms of atomic relaxations and size effects. / Singapore-MIT Alliance (SMA)

Using field theoretical methods models of strongly correlated electrons have been investigated. Application to electronic structure calculations has been made. In this thesis an attempt is made to build a bridge between first-principle band structure calculations and a theory of systems with strongly correlated electrons, by making use of perturbation theory from the atomic limit. Analyzing the total non-relativistic Hamiltonian leads to the basic model of strongly correlated systems, the Hubbard-Anderson model. In this thesis these basic models have been tested. Conclusions on delocalization and many-body aspects have been extracted from the solutions. Specifically for the lanthanides a separation of the f-system into two subsystems has resolved the discrepancy between calculated equilibrium volumes and experimental ones. The calculations are done within the Hubbard-I approximation, where it is possible to define renormalized fermion operators. The calculation is a true many-body calculation. Using perturbation theory a set of self consistent equations has been formulated, and solved, for praseodymium metal using the periodical Anderson model. The solution shows a self consistent decrease of the Hubbard U, and delocalization of the f-shell, when crucial parameters of the model are changed. The most salient feature of the models for strongly correlated electrons is the transfer of spectral weight from one energy region to another by adjusting pressure or other external parameters. The effects come from kinematic interactions that are important for strongly correlated systems. Investigations of the degenerate Hubbard model applied to the metal to insulator transition has also been made. When the degeneracy is considered, the transition to the metallic state occurs at smaller Coulomb energies. The validity of the Fermi liquid description for strongly correlated electrons has also been studied. The results show that the general behavior of the Fermi liquid state is quite robust.

The Peng-Robinson equation of state (PR EOS) is incorporated with the infinite linear association model and the monomer-dimer association model as well as two different sets of mixing rules to result in four different forms of equations of state. The reformulated PR EOS have been used to represent the vapor pressures and liquid densities of pure associating compounds. The vapor pressure and liquid density values calculated by means of the reformulated PR EOS are in good agreement with the experimental data in the literature.<p>The application of the reformulated PR EOS could be extended to represent the VLE behavior of associating systems. The capabilities of different association-incorporated EOS are compared with the Hong-Hu equation, the AMH equation and the Wilson equation, respectively. The results show that, in general, the reformulated PR EOS are superior to the Wilson equation for all tested systems with the exception of alkanol-hydrocarbon systems and at least as good as the Hong-Hu equation, the AMH equation, although the number of tested systems from Hong and Hu and Nan et al. are less than the one from the present work.<p>The excess molar enthalpies of the ethanol-n-hexane and the ethanol-cyclohexane systems at 298.15 K were measured in an LKB 2107 microcalorimeter and compared with the experimental data in the literature. Additionally, new excess molar enthalpy data, measured at 298.15 K, have been reported for the ethanol-n-hexane-cyclohexane ternary system in the present work. Smooth representations of the results are described and used to construct contours of constant enthalpy on a Roozeboom diagram. The reasonable estimates of the excess enthalpies of the three constituent-binary mixtures can be obtained from both the Liebermann-Fried model and the Flory theory. <p>Finally, an attempt has been made to represent, simultaneously, both VLE and excess enthalpy behavior of the ethanol-n-hexane and ethanol-cyclohexane systems by using the Wilson equation and one of the reformulated PR EOS. Both the reformulated PR EOS and the Wilson equation could be extended to predict the ethanol-n-hexane-cyclohexane ternary system at 298.15 K with the binary interaction parameters determined from the experimental VLE data of the three constituent-binary mixtures. The calculated results show that the reformulated PR EOS is better than or as good as the Wilson equation in predicting the excess enthalpies of selected binary and ternary systems involving one associating species. However, quantitative discrepancies with the experimental data are observed.

No description available.

The Peng-Robinson equation of state (PR EOS) is incorporated with the infinite linear association model and the monomer-dimer association model as well as two different sets of mixing rules to result in four different forms of equations of state. The reformulated PR EOS have been used to represent the vapor pressures and liquid densities of pure associating compounds. The vapor pressure and liquid density values calculated by means of the reformulated PR EOS are in good agreement with the experimental data in the literature.<p>The application of the reformulated PR EOS could be extended to represent the VLE behavior of associating systems. The capabilities of different association-incorporated EOS are compared with the Hong-Hu equation, the AMH equation and the Wilson equation, respectively. The results show that, in general, the reformulated PR EOS are superior to the Wilson equation for all tested systems with the exception of alkanol-hydrocarbon systems and at least as good as the Hong-Hu equation, the AMH equation, although the number of tested systems from Hong and Hu and Nan et al. are less than the one from the present work.<p>The excess molar enthalpies of the ethanol-n-hexane and the ethanol-cyclohexane systems at 298.15 K were measured in an LKB 2107 microcalorimeter and compared with the experimental data in the literature. Additionally, new excess molar enthalpy data, measured at 298.15 K, have been reported for the ethanol-n-hexane-cyclohexane ternary system in the present work. Smooth representations of the results are described and used to construct contours of constant enthalpy on a Roozeboom diagram. The reasonable estimates of the excess enthalpies of the three constituent-binary mixtures can be obtained from both the Liebermann-Fried model and the Flory theory. <p>Finally, an attempt has been made to represent, simultaneously, both VLE and excess enthalpy behavior of the ethanol-n-hexane and ethanol-cyclohexane systems by using the Wilson equation and one of the reformulated PR EOS. Both the reformulated PR EOS and the Wilson equation could be extended to predict the ethanol-n-hexane-cyclohexane ternary system at 298.15 K with the binary interaction parameters determined from the experimental VLE data of the three constituent-binary mixtures. The calculated results show that the reformulated PR EOS is better than or as good as the Wilson equation in predicting the excess enthalpies of selected binary and ternary systems involving one associating species. However, quantitative discrepancies with the experimental data are observed.

The structure, potential energy functions and vibrational spectra of several cyclic and bicyclic molecules have been investigated using several spectroscopic techniques and high-level ab initio and density functional theory (DFT) calculations. Laser induced fluorescence and Raman spectroscopies were used to study the conformation of 2- indanol in the electronic ground and excited states. These, along with detailed ab initio calculations, confirmed the existence of four different stable conformations with the one undergoing an intermolecular hydrogen bonding being the most stable. A theoretical two-dimensional surface in terms of the ring-puckering and the hydroxyl group internal rotation vibrations was constructed. This work was extended to obtain preliminary insights on the conformations and ring-puckering frequencies of 3-cyclopenten-1-ol using ab initio and DFT calculations. Infrared and Raman spectra were also utilized to study the structures and vibrational spectra of -crotonolactone and 2,3-cyclopentenopyridine (pyrindan). Ab initio results showed that -crotonolactone is rigidly planar in the electronic ground state and has a nearly harmonic ring-puckering potential function. The calculated vibrational levels were shown to be in very good agreement with the experimental ring-puckering frequency from vapor-phase Raman observations. The structures, vibrational spectra, and potential energy functions of several cyclic molecules were reinvestigated using high-level ab initio computations, and detailed vibrational analyses based on DFT-B3LYP calculated frequencies were also carried out. A number of new insights were presented by re-evaluating the available experimental data for several cyclopentenes, silacyclobutanes and silacyclopentenes. It was found that the vibrational spectra of some deuterated cyclopentenes possess extensive coupling between several ring modes and other low-frequency modes. Reassignments of these spectra have been proposed. Frequencies from DFT-B3LYP calculations showed very good agreement with the experimental values for silacyclobutane and its derivatives. The presence of silicon and halogen atoms did not affect the accuracy of the DFT calculations. In addition, the ring-puckering potential energy function for silacyclopent-2-ene was studied and alternative assignments of the far-infrared results were proposed. The new assignments are in good agreement with computational results. Silacyclopent-2-ene and its -1,1-d2 isotopomer were shown to be slightly puckered with barriers of less than 50 cm-1.