Vibrational frequency prediction using density functional theory

A comparison of several density functional methods for calculating vibrational frequencies is reported. Methods examined include the local S-VWN (LSDA) functional, the non-local B-LYP and B-VWN functionals and the hybrid B3-LYP and B3-P86 functionals. The split-valence polarized 6-31G* basis set has been used in all methods, The computed frequencies were compared with experimental frequencies for a set of 122 molecules (a total of 1066 frequencies). All density functional theory (DFT) methods perform well for the calculation of vibrational frequencies, with overall root mean square errors (34-48 cm(-1)) significantly less than that reported for the MP2 theory (61 cm(-1)). The two hybrid functionals -1 (B3-LYP and B3-P86) are more reliable than the S-VWN, B-LYP and B-VWN functionals. Scaling factors recommended for reproducing experimental fundamentals are 0.9833, 0.9940, 0.9820, 0.9613 and 0.9561, for S-VWN, B-LYP, B-VWN, B3-LYP and B3-P86, respectively. The performance of the various DFT methods on the calculation of zero-point energies is compared with experimental results for 24 molecules. Again, the hybrid functionals represent a significant improvement over the local and non-local density functionals.