[PyMOL] centerofmass command gives error

[Petro <sub...@kh...>]

Hi everybody
I get the following error when I try to use center of mass commanand.
Any Idea what is wrong?
Thanks.
Petro.

--------------------------------------------------------------------------KeyError
                                 Traceback (most recent call last)
Cell In[4], line 4      2 cmd.reinitialize()      3
cmd.fetch('1AKK')----> 4 cmd.centerofmass('polymer')

File ~\miniconda3\envs\pymol\lib\site-packages\pymol\querying.py:1565,
in centerofmass(selection, state, quiet, _self)   1563 model =
_self.get_model(selection, state)   1564 for a in model.atom:-> 1565
  m = a.get_mass() * (a.q or 1.0)   1566     com = cpv.add(com,
cpv.scale(a.coord, m))   1567     totmass += m

File ~\miniconda3\envs\pymol\lib\site-packages\chempy\__init__.py:82,
in Atom.get_mass(self)     80 def get_mass(self):     81     '''Given
the chemical symbol the atomic mass is returned'''---> 82     return
atomic_mass[self.symbol]
KeyError: 'D'