Static NLO responses of fluorinated polyacetylene chains evaluated with long-range corrected density functionals

As an alternative to oligomeric systems with different skeleton atoms it is shown that asymmetry introduced by substitution on a symmetric π-conjugated chain can lead to molecular systems with high non-linear optical responses. First hyperpolarizability and related properties such as the bond-length alternation parameter, dipole moment and polarizability of polyfluoroacetylene (PFA) oligomers are investigated by the Hartree-Fock, DFT and MP2 approaches. Particular attention is paid to long-range corrected DFT methods (LR-DFT). Systematic behavior of the MP2/LR-DFT ratio enables to estimate ΔβL for the eicosamer to 76 × 103 a.u. what makes PFA oligomers attractive candidates for NLO applications.