[ase-users] getting molecule symmetry number for thermochemistry

[John Kitchin]

To (probably) answer my own question, I think Table II in this link
https://cccbdb.nist.gov/thermo.asp contains the information you need.  You
do need to know the Point group of a molecule, and that can be found with
pymatgen.

Here is an example:

from ase.build import molecule
from pymatgen.symmetry.analyzer import PointGroupAnalyzer

benzene = molecule('C6H6')

PointGroupAnalyzer(Molecule(benzene.symbols,
benzene.positions)).get_pointgroup()

This yields D6h for the point group, which defines the symmetry number
(sigma) is 12 for this molecule from Table II in that link.

John

-----------------------------------
Professor John Kitchin (he/him/his)
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu



On Mon, Mar 22, 2021 at 12:17 PM John Kitchin <jkitchin at andrew.cmu.edu>
wrote:

> Hi everyone,
>
> In the ase thermochemistry module:
>
> https://wiki.fysik.dtu.dk/ase/_modules/ase/thermochemistry.html#IdealGasThermo
>
> there is a need for a symmetry number:
>
> symmetrynumber : integer symmetry number of the molecule. See, for
> example, Table 10.1 and Appendix B of C. Cramer "Essentials of
> Computational Chemistry", 2nd Ed.
>
> Does anyone know of a more accessible source for the symmetry number, or a
> python library that can calculate it?
>
> Thanks,
>
> John
>
> -----------------------------------
> Professor John Kitchin (he/him/his)
> Doherty Hall A207F
> Department of Chemical Engineering
> Carnegie Mellon University
> Pittsburgh, PA 15213
> 412-268-7803
> @johnkitchin
> http://kitchingroup.cheme.cmu.edu
>
>
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