Scaling Factors for Obtaining Fundamental Vibrational Frequencies and Zero‐Point Energies from HF/6–31G* and MP2/6–31G* Harmonic Frequencies

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Abstract
New scaling factors have been determined for obtaining fundamental vibrational frequencies and zero‐point vibrational energies from harmonic frequencies calculated at the HF/6–31G* and MP2/6–31G* levels. The scaling factors for the fundamental frequencies have been derived from a comparison of a total of 1066 calculated frequencies for 122 molecules with corresponding experimental values, while the zero‐point energy scaling factors were determined from a comparison of the computed values with the experimental zero‐point energies for a set of 24 molecules. The scaling factors recommended are, respectively, 0.8929 and 0.9427 for HF/6–31G* and MP2/6–31G* fundamental frequencies, and 0.9135 and 0.9646 for HF/6–31G* and MP2/6–31G* zero‐point energies. RMS errors were determined to be around 50 cm−1 for the HF and MP2 fundamental frequencies, and around 0.4 kJ mol−1 for the HF and MP2 zero‐point energies.