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No description available.

A busca por um conjunto de bases de alta qualidade é feita por vários grupos, pois a utilização destes conjuntos é importante para a obtenção de resultados exatos, tanto para propriedades atômicas quanto para propriedades moleculares. Os conjuntos usados neste trabalho são constituídos através da utilização do Método da Coordenada Geradora Hartree-Fock em sua versão polinomial e foram construídos de forma a permitirem uma maior flexibilidade à camada de valência do átomo, flexibilidade esta que foi proporcionada pelo número de funções que descrevem a última camada do átomo. Uma nova metodologia para a construção de conjuntos de base foi proposta neste trabalho. Esta nova metodologia diminui a busca artesanal pela busca pelos conjuntos de base introduzindo o Método Simplex em nosso programa gerador de base GENBASIS minimizando o tempo de procura por essa bases de qualidade. A aplicação destes conjuntos para estimativa de propriedades atômicas e moleculares foi feita em comparação com conjuntos de base largamente utilizados na literatura, envolvendo cálculos com vários níveis de teoria, desde o método Hartree-Fock até a Teoria do Funcional Densidade. / The search for high quality basis set is made by several groups since the quality of the basis sets is a very important factor to obtain accurate results for atomic and molecular properties. The basis sets used in this work are designed by using the polynomial Generate Coordinate Method and were constructed with the aim to improve the flexibility of a basis sets to describe the valence shell. A new methodology for the search of this basis set is proposed in this work. This new methodology makes the search for this basis set less artisanal with the introduction of the Simplex Method in our basis generator program, GENBASIS. This introduction minimizes the time used in the search for these quality basis set. The application of our basis sets in atomic and molecular calculations were compared with the most used basis sets in the literature and were performed by using different level of calculations, namely, from Hartree-Fock to Density Functional Theory.

A busca por um conjunto de bases de alta qualidade é feita por vários grupos, pois a utilização destes conjuntos é importante para a obtenção de resultados exatos, tanto para propriedades atômicas quanto para propriedades moleculares. Os conjuntos usados neste trabalho são constituídos através da utilização do Método da Coordenada Geradora Hartree-Fock em sua versão polinomial e foram construídos de forma a permitirem uma maior flexibilidade à camada de valência do átomo, flexibilidade esta que foi proporcionada pelo número de funções que descrevem a última camada do átomo. Uma nova metodologia para a construção de conjuntos de base foi proposta neste trabalho. Esta nova metodologia diminui a busca artesanal pela busca pelos conjuntos de base introduzindo o Método Simplex em nosso programa gerador de base GENBASIS minimizando o tempo de procura por essa bases de qualidade. A aplicação destes conjuntos para estimativa de propriedades atômicas e moleculares foi feita em comparação com conjuntos de base largamente utilizados na literatura, envolvendo cálculos com vários níveis de teoria, desde o método Hartree-Fock até a Teoria do Funcional Densidade. / The search for high quality basis set is made by several groups since the quality of the basis sets is a very important factor to obtain accurate results for atomic and molecular properties. The basis sets used in this work are designed by using the polynomial Generate Coordinate Method and were constructed with the aim to improve the flexibility of a basis sets to describe the valence shell. A new methodology for the search of this basis set is proposed in this work. This new methodology makes the search for this basis set less artisanal with the introduction of the Simplex Method in our basis generator program, GENBASIS. This introduction minimizes the time used in the search for these quality basis set. The application of our basis sets in atomic and molecular calculations were compared with the most used basis sets in the literature and were performed by using different level of calculations, namely, from Hartree-Fock to Density Functional Theory.

No description available.

No description available.

<p>The vertical electronic excitation energies for the narrow-bandgap polymers LBPF, EP37 and EP62 have been calculated using Density Functional Theory (DFT). Also the vertical excitation energies for the acceptor unit of LBPF have been calculated using the Hartree-Fock (HF), DFT and Coupled Cluster (CC) methods. The calculations cover the visible and infrared wave length region and two strong transitions are obtained, one corresponding to the pi to pi* transition and one corresponding to the pi to Acceptor transition. The excitation energies obtained from DFT are below the corresponding experimental results and attempts have therefore been made to perform bench-marking calculations using a hierarchy of CC methods.</p>

<p>The absorption spectra of a recently designed low-bandgap conjugated polymer has been studied using the semi-empirical method ZINDO and TDDFT/B3LYP/6-31G. The vertical excitation energies have been calculated for monomer up to hexamer. Two main absorption peaks can be seen, the one largest in wavelength corresponding to a HOMO to LUMO transition, and one involving higher order excitations. TDDFT results are red-shifted compared to the ZINDO results. Comparison with experiment yields that short conjugation lengths are dominating. This is possibly due to steric interactions between polymer chains, breaking the conjugation length. Such effects are also studied.</p>

The vertical electronic excitation energies for the narrow-bandgap polymers LBPF, EP37 and EP62 have been calculated using Density Functional Theory (DFT). Also the vertical excitation energies for the acceptor unit of LBPF have been calculated using the Hartree-Fock (HF), DFT and Coupled Cluster (CC) methods. The calculations cover the visible and infrared wave length region and two strong transitions are obtained, one corresponding to the pi to pi* transition and one corresponding to the pi to Acceptor transition. The excitation energies obtained from DFT are below the corresponding experimental results and attempts have therefore been made to perform bench-marking calculations using a hierarchy of CC methods.

The absorption spectra of a recently designed low-bandgap conjugated polymer has been studied using the semi-empirical method ZINDO and TDDFT/B3LYP/6-31G. The vertical excitation energies have been calculated for monomer up to hexamer. Two main absorption peaks can be seen, the one largest in wavelength corresponding to a HOMO to LUMO transition, and one involving higher order excitations. TDDFT results are red-shifted compared to the ZINDO results. Comparison with experiment yields that short conjugation lengths are dominating. This is possibly due to steric interactions between polymer chains, breaking the conjugation length. Such effects are also studied.