NOTE: some of this (especially the old tutorial) may be obsoleted by FFParam.
Download the "new" CGenFF tutorial (tgz archive) that was presented at CECAM's June 2012 and 2013 "Advances in Biomolecular Modelling and Simulations using CHARMM" workshops. This tutorial is fully up-to-date with recent developments, most importantly the availability of the CGenFF program at paramchem.org, and the usage of 3-point scans to determine the force constant for select bonds, angles and improper dihedrals in larger model comounds. It largely skips the details about the target data generation steps and instead focuses more on the details of the actual force field optimization. Special thanks go to Jonathan Chee Yang Loh, whose contributions are marked "jon" in the tutorial files.
Download the accompanying slide show (recommended!) The first part of this presentation is about the (then) state of the art of the CHARMM force field; please skip to slide 76 for the actual tutorial.
Note: the CGenFF topology and parameter files included in these tutorials cannot be assumed to be up-to-date! For production calculations, download the latest CGenFF version!
Current CGenFF version
The current CGenFF version can be downloaded as part of the larger CHARMM additive force field.