VMD-L Mailing List

From: Mayne, Christopher G (cmayne2_at_illinois.edu)
Date: Fri Dec 06 2013 - 14:27:18 CST

Christian,

Parameterization of improper terms is still on our list of things to do but we haven't gotten there yet. For the reasons stated before we've been hard at work on some other features.

Regards,
Christopher Mayne

On Dec 6, 2013, at 11:12 AM, Christian Jorgensen wrote:

Hi there,

I'm wondering if as of Dec. 2013 there is an update regarding the
feasibility of parametrising improper torsions in FFTK?

Thank you in advance

Francesco,

Currently ffTK does not support the parameterization of improper terms (it's on the list). It is of note; however, that there are very few cases in which improper terms are required for CGenFF (e.g. carbonyls, planar non-cyclic nitrogens). Aromatics generally do not require improper angle terms because the torsion potentials are stiff, along with the additional constraints of bonded terms within a cyclic context. It's worth taking a look through CHARMM and CGenFF parameters to see exactly there improper terms are employed and where they are not (I was surprised at how few chemical groups require them).