[gmx-users] Multiple torsional parameters

[Anton Feenstra]

Pedro Alexandre Lapido Loureiro wrote:
> Hi,
> 
> I am implementing the lipid force field of Smondyrev & Berkowitz (J Comp Chem 
> 20, 531 - 1999).
> The problem is they use two expressions for one dihedral, such as:
> LC2  LC2O    1  0.0   5.8576   3
> LC2  LC2O    1 180.0  4.184    1
> I have built my .top file in this way.
> When I run grompp, there is a warning saying the former parameters will be 
> overridden and the latter will be used.
> How can I solve this?
> (Sorry if a matter like this has been already discussed in the list...)

You are probably defining two dihedral *types* for the same pair of atoms.
That won't work. What you will need to do, is add another dihedral to the
.rtp, .itp or .top of your lipid, and specify explicit parameters (or an
explicit type, like in the G43a* ff's) for both of them.


-- 
Groetjes,

Anton
  _____________ _______________________________________________________
|             |                                                       |
|  _   _  ___,| K. Anton Feenstra                                     |
| / \ / \'| | | Dept. of Pharmacochem. - Vrije Universiteit Amsterdam |
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