I've just installed NAST with C2A. I also have OpenMM and pyopenmm installed. I don't seem to have the chem.openmm module.
from the 6TNA_MD example :
$ python ./runTest.py
Traceback (most recent call last):
File "./runTest.py", line 20, in <module>
import simtk.nast.molecule as molecule
File "/programs/x86_64-linux/python/2.7.12/lib/python2.7/site-packages/simtk/nast/molecule.py", line 20, in <module>
import simtk.chem.openmm as mm
ImportError: No module named chem.openmm
Is this included in some other package or a different version ? I am using openmm 7.0.1.