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1. What is Shermo?

Shermo program is a free, general, easy-to-use and flexible code for calculating molecular thermochemistry data based on ideal gas assumption. Although most quantum chemistry programs have their own codes used to calculate thermochemistry data after performing frequency analysis, they are not as powerful and flexible as Shermo, and usually their outputs are inconvenient to read.

Features of Shermo

  • Output file of frequency analysis task of various quantum chemistry programs can be used as input file, including Gaussian, ORCA, GAMESS-US, NWChem, CP2K and xtb. Other programs can also utilize Shermo to compute thermochemistry data as long as they can generate the .shm file defined by Shermo.
  • All common thermochemistry quantities can be calculated, including internal energy (U), enthalpy (H), entropy (S), constant volume heat capacity (CV), constant pressure heat capacity (CP) and partition function (q).
  • Contributions of translation, rotation, vibration, electron to various thermochemistry properties are outputted in a very compact and clear format. Contribution of every vibrational mode can also be printed to understand their influences on the calculated properties.
  • Temperature and pressure can be easily scanned.
  • Conformation/configuration weights and weighted thermodynamic data can be obtained.
  • Thermochemistry properties can be calculated based on the standard rigid-rotor harmonic oscillator (RRHO) model. While in order to much better deal with low frequencies, two kinds of quasi-RRHO treatments can also be used: (1) Raising lower frequencies to a specific value (2) Interpolation between harmonic oscillator and free-rotor approximations (for entropy part, and can also be for internal energy part, corresponding to Grimme’s and Minenkov’s models, respectively).
  • Imaginary frequencies are allowed to be treated as real frequencies.
  • Frequency scale factors for ZPE, heating contribution to internal energy, entropy and heat capacity can be individually specified.
  • Point group and rotational symmetry number can be automatically assigned.
  • Variation of Gibbs free energy due to concentration change from current state to specific state can be taken into account.
  • Shermo can not only run in interactive mode but also run in command-line mode, thus it can be easily incorporated into shell script for batch processing.
  • Very easy to use. The program can be used without installation, and users do not need to prepare any running environment like Python.

Citation of Shermo

If Shermo is employed in your study, please cite it in your paper as follows:

Tian Lu, Qinxue Chen, Shermo: A general code for calculating molecular thermodynamic properties, Comput. Theor. Chem., 1200, 113249 (2021) DOI: 10.1016/j.comptc.2021.113249

Seeking help

If you encountered any problem in using Shermo, please feel free to contact me via E-mail (sobereva@sina.com). You can also post your question on quantum chemistry board of computational chemistry commune forum (http://bbs.keinsci.com/forum-103-1.html), I will always timely reply to you.