Conjuntos de bases gaussianas: aplicações em cálculos de constantes espectroscópicas e rotação ótica

• Ano de defesa: 2012
• Autor(a) principal: Campos, Cesar Turczyn
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Espírito Santo; BR; Doutorado em Física; Centro de Ciências Exatas; UFES; Programa de Pós-Graduação em Física
• Palavras-chave em Português: Conjuntos de bases gaussianas (Mecânica quântica); Rotação ótica; Átomos; Moléculas; Atomização; Física; 53
• Link de acesso: http://repositorio.ufes.br/handle/10/7478

Segmented all-electron contracted sextuple zeta valence plus polarization function (6ZP) basis sets for the elements from H to Ar were constructed to be used in conjunction with the nonrelativistic and Douglas-Kroll-Hess (DKH) Hamiltonians. The scalar relativistic effect at the coupled cluster (CC) level of theory on atomization energy for a sample of molecules was discussed. Additional improvements in the atomization energies were achieved by applying corrections due to core/valence correlation, atomic spin-orbit effects, and addition of tight d and f functions on second-row elements. This leads to estimates for the heat of formation of gaseous boron and carbon tetrafluoride. With the purpose to have a better description of some molecular properties, the non relativistic and relativistic segmented all-electron contracted double, triple, quadruple, quintuple, and sextuple zeta valence plus polarization function (XZP and XZP-DKH, X= D, T, Q, 5, and 6) basis sets for the elements from H to Ar were augmented with high-exponent d “inner polarization functions”, which were optimized in the molecular environment at the M?ller-Plesset secondorder level. At the CC level of theory, the effect of including tight d functions in these elements was found to be essential to improve the agreement between theoretical and experimental zero-point vibrational energy (ZPVE) and atomization energy. For all molecules studied, the ZPVE errors are always smaller than 0.5%. Additional improvements in the atomization energies were achieved by applying corrections due to core/valence correlation and atomic spin-orbit effects. This leads to estimates for the atomization energies of various compounds in gaseous phase. The largest error (1.2 kcal/mol) occurs for SiH4. Finally, using the hierarchical sequence of augmented XZP (AXZP, X = D, T, and Q) for the atoms from H to Ar in conjunction with the B3LYP, PBE1PBE, M06, and M06-2X functionals, a systematic study of Gaussian basis set convergence on frequency dependent optical rotation ([?]?) calculations of thirteen rigid chiral molecules at their equilibrium geometries were xvii reported. By direct calculations or by fitting the directly calculated values through one extrapolation scheme, estimates of complete basis set limits were obtained. These limits can be used as reference values to calibrate further density functional theory calculations