Annotate an OpenMM .xml force field file with SMARTS-based atomtypes:

<ForceField>
 <AtomTypes>
  <Type name="opls_135" class="CT" element="C" mass="12.01100" def="[C;X4](C)(H)(H)H" desc="alkane CH3"/>
  <Type name="opls_140" class="HC" element="H" mass="1.00800"  def="H[C;X4]" desc="alkane H"/>
 </AtomTypes>
</ForceField>

Apply the forcefield to arbitrary chemical topologies. We currently support:

• OpenMM.Topology
• ParmEd.Structure
• mBuild.Compound

from foyer import Forcefield
import parmed as pmd

untyped_ethane = pmd.load_file('ethane.mol2', structure=True)
oplsaa = Forcefield(forcefield_files='oplsaa.xml')
ethane = oplsaa.apply(untyped_ethane)

# Save to any format supported by ParmEd
ethane.save('ethane.top')
ethane.save('ethane.gro')

Check out our example template for disseminating force fields: https://github.com/mosdef-hub/forcefield_template

Various sub-portions of this library may be independently distributed under different licenses. See those files for their specific terms.

This material is based upon work supported by the National Science Foundation under grants NSF ACI-1047828 and NSF ACI-1535150. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.