Reparameterized Semiempirical Anharmonic IR Spectra of Neutral PAHs: Benchmarking and Predictions for PAHs with More than Five Rings.

Recently developed, reparameterized PM6 methods can reproduce experimental polycyclic aromatic hydrocarbon (PAH) IR spectra with nearly the same accuracy as state-of-the-art quantum chemical methods but for notably less computational cost. The use of the () semiempirical method (as opposed to () for density functional theory or () for the most accurate coupled cluster theory) allows for full, explicit, quartic force field (QFF), anharmonic computations on PAHs. The anharmonicity also predicts the combination band and overtone frequencies in addition to the fundamentals.