The consistency analysis of different semiempirical calculations on second- and third-order nonlinear optical properties of donor-acceptor chromophores containing α-cyan

The static and frequency dependent average polarizability (<α>), first- and second-hyperpolarizabilities (<β> and <γ>) and HOMO and LUMO energies of donor-acceptor chromophores containing α-cyan (1a-c) have been investigated by using the AM1, MNDO, MNDO-d, PM3, RM1 and PM6 methods within a time-dependent Hartree-Fock (TDHF) approaches. The electronic properties of 1a-c have been reported by employing two-state model calculated at ZINDO/S-SCI, PM3-SCI and RM1-SCI methods. Also, the molecular hardness (η) and electronegativity (χ) parameters have been obtained by using molecular frontier orbital energies. The <α>, <β>, <γ> HOMO, LUMO energies, η and χ parameters have been investigated with respect to the choice of different semiempirical methods. The variation graphics of β, β0, η and χ parameters according to the different semiempirical methods are presented. Furthermore, the variation graphics of β0 with regard to the μeg, Δμ and λeg are displayed. The frontier molecular orbital and electrostatic potential pictures of 1a-c using ZINDO/S-SCI level have been examined. The results of 1a-c display significant second- and third-order molecular nonlinearity.