[gmx-users] :a grompp problem using a ffamber port

Anton Feenstra feenstra at few.vu.nl
Thu Oct 27 09:38:30 CEST 2005


David Mobley wrote:

> Sara,
> 
> You might want to correspond with the Pande group on this, as they're the
> ones who put out the port.
> 
> I had a similar problem with Cl- ions and, as a temporary solution, modified
> the ions.itp file in the top directory to have an #ifdef _FF_AMBER section
> specifying the appropriate ion definitions (copied from earlier in the
> ions.itp file but changing the atom types to the amber atom types -- i.e.
> CL- is amber94_30). My conclusion was that no ion parameters were being
> loaded when _FF_AMBER was defined, so I thought this was necessary. I
> remember corresponding with Eric Sorin (Pande group) on this and he had some
> alternative method of setting up systems where this wasn't a problem, I
> think.
> 
> Anyway, you'll probably need to talk to them, as the Amber FF is not a part
> of Gromacs, so in general you probably won't get support from this list.

Aside from that, using the parameters from ions.itp, which are intended 
to be used with the Gromos forcefields (that is why the #ifdef is 
there!), with the Amber ff instead is probably a bad idea. I'd recommend 
checking the parameters carefully with the ion parameters from Amber 
itself (beware of unit conversions, e.g., A vs nm and cal vs J).


-- 
Groetjes,

Anton

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