Harmonic frequency scaling factors for Hartree-Fock, S-VWN, B-LYP, B3-LYP,B3-PW91 and MP2 with the Sadlej pVTZ electric property basis set

Scaling factors for obtaining fundamental vibrational frequencies from harm onic frequencies calculated at six of the most commonly used levels of theo ry have been determined from regression analysis for the polarized-valence triple-zeta (pVTZ) Sadlej electric property basis set. The Sadlej harmonic frequency scaling factors for first- and second-row molecules were derived from a comparison of a total of 900 individual vibrations for 111 molecules with available experimental frequencies. Overall, the best performers were the hybrid density functional theory (DFT) methods, Beckes three-parameter exchange functional with the Lee-Yang-Parr fit for the correlation functio nal (B3-LYP) and Becke's three-parameter exchange functional with Perdew an d Wang's gradient-corrected correlation functional (B3-PW91). The uniform s caling factors for use with the Sadlej pVTZ basis set are 0.9066, 0.9946, 1 .0047. 0.9726, 0.9674 and 0.9649 for Hartree-Fock, the Slater-Dirac exchang e functional with the Vosko-Wilk-Nusair fit for the correlation functional (S-VWN), Becke's gradient-corrected exchange functional with the Lee-Yang-P arr fit for the correlation functional (B-LYP), B3-LYP. B3-PW91 and second- order Moller-Plesset theory with frozen core (MP2(fc)), respectively. In ad dition to uniform frequency scaling factors, dual scaling factors were dete rmined to improve the agreement between computed and observed frequencies. The scaling factors for the wavenumber regions below 1800 cm(-1) and above 1800 cm(-1) are 0.8981 and 0.9097, 1.0216 and 0.9857, 1.0352 and 0.9948, 0. 9927 and 0.9659, 0.9873 and 0.9607, 0.9844 and 0.9584 for Hartree-Fock, S-V WN, B-LYP, B3-LYP, B3-PW91 and MP2(fc), respectively. Hybrid DFT methods al ong with the Sadlej pVTZ basis set provides reliable theoretical vibrationa l spectra in a cost-effective manner.