Computational thermochemistry: Automated generation of scale factors for vibrational frequencies calculated by electronic structure model chemistries

Haoyu S. Yu, Lucas J. Fiedler, I. M. Alecu, Donald G. Truhlar

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


We present a Python program, FREQ, for calculating the optimal scale factors for calculating harmonic vibrational frequencies, fundamental vibrational frequencies, and zero-point vibrational energies from electronic structure calculations. The program utilizes a previously published scale factor optimization model (Alecu et al., 2010) to efficiently obtain all three scale factors from a set of computed vibrational harmonic frequencies. In order to obtain the three scale factors, the user only needs to provide zero-point energies of 15 or 6 selected molecules. If the user has access to the Gaussian 09 or Gaussian 03 program, we provide the option for the user to run the program by entering the keywords for a certain method and basis set in the Gaussian 09 or Gaussian 03 program. Four other Python programs,, input6,, and, are also provided for generating Gaussian 09 or Gaussian 03 input and PBS files. The program can also be used with data from any other electronic structure package. A manual of how to use this program is included in the code package. Program summary Program title: FREQ Catalogue identifier: AFBH_v1_0 Program summary URL: Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland at or from Truhlar group software page at Licensing provisions: GNU GPL v3 No. of lines in distributed program, including test data, etc.: 3013 No. of bytes in distributed program, including test data, etc.: 212537 Distribution format: tar.gz Programming language: PYTHON. Computer: Any computer with PYTHON compiler. Operating systems: Linux, Unix. Classifications: 16.3, 23. External routines: Gaussian 03 or Gaussian 09 (see “Restrictions”). Nature of problem: Optimization of property-specific scale factors for vibrational frequencies for a specific electronic model chemistry. Solution method: The method is based on minimizing the root-mean-square deviation between a set of zero-point energies derived from harmonic vibrational frequencies (either provided by the user or computed on the fly) and their experimentally determined counterparts. Restrictions: In order to compute the electronic model chemistry's harmonic zero-point energies on the fly, the user must have access to the Gaussian 03 or Gaussian 09 program. If the electronic model chemistry's zero-point energies are read in, no other program is required. Additional comments: After opening the FREQ.tar.gz file, the user will find a file which can be used to run all the programs to obtain the scaling factors for a user-chosen electronic structure model chemistry. Running time: Less than a second if the user provides the zero-point energies; if zero-point energies are to be computed, the running time depends on the electronic model chemistry used to compute them as well as the efficiency of the Gaussian 09 program, in our test we obtain the results within 10 min by using one node with eight processors for each Gaussian 09 input on Minnesota Supercomputing Institute's Mesabi supercomputer.

Original languageEnglish (US)
Pages (from-to)132-138
Number of pages7
JournalComputer Physics Communications
StatePublished - Jan 1 2017

Bibliographical note

Funding Information:
The authors are grateful to the CPC Program Librarian, Carol Phillips, for suggestions that improved the program. This material is based on work supported by the U.S. Department of Energy, Office of Basic Energy Sciences , under grant no. DE-SC0008666 .


  • Force constants
  • Frequencies
  • Fundamental frequency
  • Harmonic approximation
  • Molecules
  • Scale factors
  • Vibrations
  • Zero-point energy

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