The prediction of Raman spectra by density functional theory. Preliminary findings

We report the first calculations of Raman vibrational intensities by density functional theory, implemented within the Q-Chem program. Local (S-VWN) and gradient-corrected (B-LYP) DFT results are compared with experimental and Hartree-Fock results for the N2, HF and C2H6 molecules. Preliminary indications are that local DFT compares less favorably to experiment than either Hartree-Fock or gradient-corrected DFT. The Hartree-Fock and B-LYP results are generally similar except for the HF molecule, where B-LYP is somewhat better. For all methods, best results were obtained by augmenting the basis set with diffuse polarization functions.