Proper torsion parameters missing?

From: Heike Meiselbach <>
Date: Thu 23 Jan 2003 20:05:05 +0100 (MET)

Hi Amberlist,

I would like to perform a FEP with an organik molecule. I have problems
when saving the perturbation topology and crd file.
I have created a dummy parameter file (frcmod), with MASS, BOND, etc.
I loaded this file in xleap (x = loadamberparams frcmod) and want to
save my unit. But I get the following error:
*** Proper torsion parameters missing ***
 atom names: C41-C5-C51-C1B
 atom types: CT-CT-CT-CA =pert=> CT-CT-CA-CA
Please add a dummy parameter of multiplicity 2
for the non-pert types to your parameter set.
 - e.g. CT-CT-CT-CA 1 0.0 0. 2.
(This is because multiple torsional potentials may apply to a
single torsion, and each is perturbed individually in gibbs.)

This message is repeated several times.
I added the example given by the error message to the frcmod, but
still receive the same error message.

Does anyone have an idea as to how I can solve this problem? Any help
would be appreciated.

Received on Thu Jan 23 2003 - 11:05:05 PST
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