Rotation number for single atoms has changed from `inf` to `None`

[Andrew-S-Rosen]

Code snippet

from emmet.core.symmetry import PointGroupData
from ase.build import molecule
from pymatgen.core import Molecule

mol = Molecule.from_ase_atoms(molecule("H"))
sigma = PointGroupData().from_molecule(mol).rotation_number
print(sigma)

What happened?

In #1350, the rotational symmetry number for a single atom changed from a value of inf to None. I'm not sure if this was intentional or not. I suppose None is more accurate than inf, although I'd argue that perhaps 1 is more accurate than either. Personally, I am fine with this change, but I did want to alert @esoteric-ephemera.

Version

0.86.2

Which OS?

• MacOS
• Windows
• Linux

Log output

[esoteric-ephemera]

Looking at the table of rotation numbers to symmetry groups, I think the number is just the number of symmetry-preserving rotation operations. For a point-like isolated atom with spherical symmetry, that number should then be infinite