Benchmark Study of Ground-State Raman Spectra in Conjugated Molecules

In this work, we compare calculated and experimental off-resonance Raman spectra for a series of substituted benzene and thiophene derivatives in the ground state. We benchmark a variety of approximate density functionals following the "Jacob's Ladder" hierarchy of chemical accuracy, as well as second-order Møller-Plesset perturbation theory. The Raman calculations at all levels of theory consistently overestimate the intensities of high-frequency vibrations relative to the lower frequency region of the spectrum. Although all methods provide comparable estimates of relative intensities for all compounds, the hybrid B3LYP and TPSSh functionals perform 5-19% better than the other methods in terms of mean unsigned error and 2-24% better in the standard deviation of the error. Both functionals also give band positions accurate to within about ±10 cm^-1 of the experimental frequencies.