ParamChem technologies


CGenFF program

The CHARMM General Force Field (CGenFF) program at performs atom typing and assignment of parameters and charges by analogy in a fully automated fashion. Atom typing is done by a deterministic programmable decision tree. Assignment of bonded parameters is based on substituting atom types in the definition of the desired parameter. A penalty is associated with every substitution and the existing parameter with the lowest total penalty is chosen as an approximation for the desired parameter; the "penalty score" is returned to the user as a measure for the accuracy of the approximation. Charges are assigned using an extended bond-charge increment scheme that is able to capture short- and medium-range inductive and mesomeric effects.

  CGenFF program links

  CGenFF force field links

lsfitpar Program

The lsfitpar program is the C reference implementation of our restrained Linear Least Squares (LLS) procedure to simultaneously fit all the bonded parameters in a Class I force field. The restraining strategy used in this methodology is novel and overcomes robustness issues in the LLS fitting of bonded parameters while minimally impacting the fitted values of well-behaved parameters. The program is available to the community under the Affero GPL.


ParamChem cyberinfrastructure (development halted in late alpha stage)

This is the main middeware and back-end software stack of the ParamChem project, the development of which was halted in a late alpha stage. Please contact Sudhakar Pamidighantam for more info.


Paramberoo GUI (development halted in late alpha stage)

This is a fork of Vladislav Vasilyev's Jamberoo GUI, with features to allow novice ParamChem users to start force field parameter optimization on arbitrary organic molecules of interest. Its development was halted in a late alpha stage. Please contact Ning Shen for more info.


  • Screenshots (coming soon).

ParamCAD GUI (work in progress)

This is our graphical interface for expert users, built de novo for force field parameter optimization. Development of this project is in progress, and the direction in which it will evolve depends largely on interest from 3rd parties. Please contact R. Michael Sheetz for more info.


  • Screenshots (coming soon).