For the former, an algorithm was implemented that reads the parameters and the coordinates from the xml and pdb input files respectively, and returns formatted AMBER files (prm7/rst7) that contain exactly the same information and can be parsed by SOMD. Geometric combination rules have also been implemented in SOMD to support OPLS-style force fields. Further information and comparison of single point energies between OpenMM and SOMD are provided in the Supporting Methods.