Database of Frequency Scale Factors for Electronic Model Chemistries

maintained by S. Kanchanakungwankul, J. Zheng, I. M. Alecu, B. J. Lynch, Y. Zhao, and D. G. Truhlar



When vibrational frequencies are calculated by electronic structure theory, they can often be improved by scaling, and it is useful to have scale factors for doing this. Such scale factors depend on the level of electronic structure theory and the one-electron basis set, the combination of which we denote as an electronic model chemistry. Frequencies may be scaled in various ways. For example, one may scale them to try to reproduce the true vibrational harmonic frequencies (H), the observed vibrational fundamental frequencies (F), or the vibrational zero-point energy (ZPE). The aim of this database is to provide reliable scale factors that can be used in conjunction with the tabulated electronic model chemistries to accurately reproduce the aforementioned experimental properties. In each version of the database, the recommended citations for the scale factors are also tabulated. In cases where the scale factors are published, it is preferred that users refer to the archival journal article(s) rather than just citing this Web page. The methods employed to optimize the scale factors in each version of the database are referenced or explained therein.


The latest versions of our frequency scale factor database is version 5:


Database of Frequency Scale Factors for Electronic Model Chemistries Version 5

Old versions are not needed for any practical reason because version 5 includes all scale factors, but the old versions are archived here:


If you do not find the scale factor you need you in the latest database you may calculate a scale factor for your model chemistry by using the FREQ program at


  1. "Computational Thermochemistry: Scale Factor Databases and Scale Factors for Vibrational Frequencies Obtained from Electronic Model Chemistries," I. M. Alecu, J. Zheng, Y. Zhao, and D. G. Truhlar, J. Chem. Theory Comput. 6, 2872-2887 (2010). DOI URL Electronic Reprint URL Supporting information

This document last modified on July 22, 2021
Updated by:  Software Manager