Estudo dos efeitos dos conjuntos de base sobre a descrição da estrutura eletrônica molecular e do espalhamento elétron-molécula: H2, N2 e O2
This paper presents an analysis of the influence of basis sets on the description of the molecular electronic structure and in calculation results of electron-molecule scattering applied to molecules of hydrogen, nitrogen and oxygen. Secondly, comparisons are presented between semiempirical methods...
| Autor principal: | Azzolini, Natielle |
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| Formato: | Trabalho de Conclusão de Curso (Graduação) |
| Idioma: | Português |
| Publicado em: |
Universidade Tecnológica Federal do Paraná
2020
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| Assuntos: | |
| Acesso em linha: |
http://repositorio.utfpr.edu.br/jspui/handle/1/15293 |
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| Resumo: |
This paper presents an analysis of the influence of basis sets on the description of the molecular electronic structure and in calculation results of electron-molecule scattering applied to molecules of hydrogen, nitrogen and oxygen. Secondly, comparisons are presented between semiempirical methods for the application of two software: GAMESS and MOPAC. Total and orbital energies were calculated by the HF-SCF method, the static potential via ab initio method, potential-model correlation-polarization and absorption and elastic cross sections differential by Method of Continued Fractions, from a wide range of atomic bases. The cross sections were calculated for the incidence energy of 30 and 100 eV, in approaches the SEP-CoPolP and SEP-AbP, respectively. The effects of basis sets for scattering calculations were evaluated by Principal Component Analysis (PCA), which proved to be efficient to explain 83.6 to 99.7% of the total variance of the data, through two principal components. The Method of Continued Fractions showed excellent agreement with experimental data for e-H2 scattering, and a good agreement with the experimental data for e-N2. The interaction potentials described well the expected behavior. In all cases, base sets MINI for H2 and STO-6G for N2 and O2, showed anomalous behavior in relation to others. In this sense, the cross sections were sensitive to a greater or lesser extent, to these differences in potential of interaction associated with it. Moreover, in most cases, correlations were observed and detected by PCA analysis between basis sets DZ, ADZ and UGBS (and STO-6G, in the case of H2) and between the DZP and 6-311++G(2d, 2p) basis sets (and Base1, in the case of N2). Regarding the molecular electronic structure, we obtained a continuous improvement of the molecular total energies with increasing sets of bases, as expected. However, the semiempirical methods analogous behavior was observed. In general, the best results were obtained by MNDO and AM1. Overall, there was good and reasonable agreements between the orbital energies obtained via ab initio and semiempirical methods. The inversions energy occurred between orbital 1πu and 3σg for N2, were linked to the neglect of the effects of electron correlation, and therefore is in an intrinsic failure of the HF-SCF method. In addition, we obtained a good agreement between the molecular properties calculated by GAMESS and MOPAC software in semiempirical approach. |
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