Mestrado em Física (IF)
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Item Cálculos de propriedades elétricas da metanol incluindo correções vibracionais e correlação eletrônica(Universidade Federal de Goiás, 2009) Dutra, Adriano da Silva; Castro, Marcos Antônio de; http://lattes.cnpq.br/3500875789893244In this work we report results for the polarizability, and first and second hyperpolariz- abilities of the methanol molecule including vibrational corrections and electron correlation effects. The Vibrational corrections were computed using the perturbation theoretic approach of Bishop and Kirtman and the electron correlation effects were taken into account through the CCSD(T) method implemented in the GAUSSIAN 03 program. The electronic contributions to the electric properties were calculated using the finite-field scheme. Comparisons of our CCSD(T) values with previous TDHF result show that the electron correlation effects, are in general, important. An analysis of the importance of the vibrational corrections shows that the zpva correction is not negligible, specially for the hyperpolarizabilities. The pv correction is, in general, important and the double-harmonic approximation is suitable to the calculation of this correction for most of the nonlinear optical processes studied.Item Correções vibracionais para as segundas hiperpolarizabilidades de clusters AlnPn(Universidade Federal de Goiás, 2015-03-25) Feitoza, Luan da Silva; Castro, Marcos Antônio de; http://lattes.cnpq.br/3500875789893244; Castro, Marcos Antônio de; Varella, Márcio Teixeira do Nascimento; Georg, Herbert de CastroThis work presents the vibrational contributions for the static and dynamic second hyperpolarizabilities of the clusters Al2P2, Al3P3, Al4P4, Al6P6 and Al9P9. The optimized geometries and the calculations of harmonic vibrational frequencies, dipole moments ( ), polarizabilities ( ) and first hyperpolarizabilities ( ) were performed at the MP2 level along with the basis set aug-cc-pVDZ using the GAUSSIAN 09 program. The calculations of vibrational corrections were performed using the perturbation theoretical method of Bishop and Kirtman (PT) and a variational methodology (VAR) developed in our research group. The outcomes show that the vibrational corrections have the same magnitude order of electronic contributions, therefore cannot be neglected. The results also showed that PT method is sufficient to obtain the most relevant terms, [ 2] and [ ], but there are limitations to compute the term [ 2 ], which is related to the system anharmonicities. The vibrational corrections by atom have a similar convergence trend to that exhibited by the related electronic contribution by atom as the number of atoms increases. The nonlinear optical processes IDRI, dc-SHG and dc-K were studied for the dynamic vibrational corrections. Dynamic results reflect static vibrational results. In particular, the frequencies of the modes that contribute most in the static limit are associated with the peaks of the second dynamic hyperpolarizability.Item Hiperpolarizabilidades do sal de lítio de piridazina dopado com cálcio (Li - H3C4N2 ... Ca)(Universidade Federal de Goiás, 2015-10-23) Silva Filho, Suélio Marques da; Castro, Marcos Antônio de; http://lattes.cnpq.br/3500875789893244; Castro, Marcos Antônio de; Martins, João Batista Lopes; Oliveira, Guilherme Colherinhas deIn this work we present results for static and dynamic hyperpolarizabilities of the lithium salt of pyridazine calcium doped LiH3C4N2 Ca. The geometry of this molecule was optimized at the MP2 level with the cc-pVQZ basis set of functions through the Gaussian 09 program. We analyzed the level of electronic correlation and optimized a basis set of functions to calculate the hyperpolarizabilities of this molecule. The properties of interest were calculated analytically at the CCSD level with the optimized basis set using the response theory implemented in DALTON 2013 program. The results showed that the doping of the lithium salt of pyridazine is very important for increasing the value of the second hyperpolarizability. When doped with calcium, its value is of the order of 106 atomic units (au), which indicates that this molecule has the potential to be used in nonlinear optical materials. The dependence in relation to the frequency was studied for the following nonlinear optical processes: dc-P and SHG related with the first hyperpolarizability; dc-K, IDRI, dc-SHG and THG related with the second hyperpolarizability.Item Correções vibracionais para as (hiper)polarizabilidades do sal de lítio de piridazina Li -H3C4N2(Universidade Federal de Goiás, 2014-02-03) Silveira Júnior, Orlando José; Castro, Marcos Antônio de; http://lattes.cnpq.br/3500875789893244; Castro, Marcos Antônio de; Mundim, Kleber Carlos; Pontes, Renato BorgesIn this work we report dynamic values for the (hyper)polarizabilities of lithium salt of pyridazine Li H3C4N2 including vibrational corrections. The electronic contributions were computed analytically at the single and double coupled cluster level (CCSD) through response theory, as implemented in the DALTON program, with the aug-cc-pVDZ basis set. The calculations for the vibrational corrections were carried out at the second-order Møller-Plesset level (MP2) by means of the perturbation theoretical method of Bishop and Kirtman and also using a variational approach proposed here. The results obtained for the zero-point vibrational average (zpva) corrections show that the two approaches lead practically to the same results, accounting for 2 and 6 % of the corresponding electronic contributions for polarizability and _rst hyperpolarizability, respectively. The results ob-tained show that, at the static limit, the pure vibrational corrections for the polarizability and _rst and second hyperpolarizabilities have the same order of magnitude of the corre-sponding electronic contributions. Comparisons between the results obtained through the two methods show that the perturbation theoretical method is not suitable to treat the system studied, whereas the variational methodology presented seems to be an alternative approach to treat anharmonic systems.