The dynamical shell model implemented in DL_POLY_2 is not designed
to work with rigid molecules. This error results if these two options
are simultaneously selected.
Action:
In some circumstances you may consider overriding
this error message and continuing with your simulation. For example
if your simulation does not require the polarisability to be a feature
of the rigid species, but is confined to free atoms or flexible
molecules in the same system. The appropriate error trap is found in
subroutine SYSDEF.