Transferable Scaling Factors for Density-Functional Derived Vibrational Force-Fields

by Rauhut, Guntram; Pulay, Peter

Density functional theory (DFT) using the 6-31G* basis set and two nonlocal exchange-correlation functionals (Becke-Lee-Yane-Parr [B-LYP] and the three-parameter compound function of Becke [B3-LYP]) has been used for the calculation of vibrational force fields of a set of 31 organic molecules including a wide range of functional groups. The calculated force constants have been scaled to experimental vibrational frequencies by using (a) an overall scaling constant and (b) a set of 11 factors paying respect to the different kinds of internal coordinates. The comparison of the scaled fundamental frequencies with experiment shows that density functional theory is a reliable tool for the interpretation of IR spectra. The uncorrected DFT frequencies and force constants approximate the experimental ones in a much more uniform fashion than does Hartree-Fock theory. Nevertheless, the use of multiple scale factors leads to further significant improvement. The scaled B3-LYP results are superior to the B-LYP ones, even though the unsealed B-LYP frequencies are, through error cancellation, slightly better than the B3-LYP ones. The reliability of scaled force fields is demonstrated by comparing the calculated and experimental vibrational spectra of aniline.

Journal
Journal of Physical Chemistry
Volume
99
Issue
10
Year
1995
Start Page
3093
ISBN/ISSN
1520-5215; 0022-3654
DOI
10.1021/j100010a019