New Scale Factors for Harmonic Vibrational Frequencies Using the B3LYP Density Functional Method with the Triple-delta Basis Set 6-311+G(d,p)

摘要

We have calculated optimal frequency scaling factors for the B3LYP/ 6-311 +G(d,p) method for fundamental vibrational frequencies on the basis of a set of 125 molecules.Using the new scaling factor,the vibrational frequencies calculated with the triple-delta basis set 6-311+G(d,p) give significantly better accuracy than those calculated with the double-delta 6-31G(d) basis set.Scale factors were also determined for low-frequency vibrations using the molecular set of 125 molecules and for zero-point energies using a smaller set of 40 molecules.We have studied the effect on the calculated vibrational frequencies for various combinations of diffuse and polarization functions added to the triple-delta 6-311G basis set.The 6-311+G(d,p) basis set is found to give almost converged frequencies for most molecules,and we conclude that our optimum scaling factors are valid for the basis sets 6-311G(d,p) to 6-311++G(3df,3pd).The new scale factors are 0.9679 for vibrational frequencies,1.0100 for low-frequency vibrations,and 0.9877 for zero-point vibrational energies.