Gaussian density functional calculations on the allyl and polyene radicals: C₃H₅ to C₁₁H₁₃

The electronic structure of the allyl radical C₃ H₅ and the polyene radicals C₅ H₇, C₇ H ₉, C₉H₁₁, and C₁₁H₁₃ have been calculated using the linear combination of Gaussian-type orbitals-local spin density method. In contrast to the results obtained using the Hartree-Fock model, which show large errors, the geometries are in excellent agreement with multiconfiguration self-consistent-field calculations and with experiment. LSD yields a C_2v symmetry for the allyl radical, while the polyenes C₅H₇ to C₁₁H₁₃ have C-C bonds alternating between single and double bonds. The harmonic vibrational frequencies were calculated for the allyl radical and C₅H₇ (the 1,4-pentadienyl radical). The unscaled vibrational frequencies calculated for the allyl radical are in excellent agreement with experiment.