[gmx-users] invalid angle type 0

[Mark Abraham]

Bing Bing wrote:
> Dear all,
> I 've prepared POPC  and protein with ffG53a6 forcefield. I've  also built
> the ligand in the protein with ffG53a6, but it is not working. Many atom
> types in the ligand which i work on is not found in ffG53a6*.itp but if i
> change the forcefield to ffgmx, it work fine.
> I have tried to add-in those unrecognize atomtype into the ffG53a6bon.itp
> and ffG53a5nb.itp from ffgmx*.itp.

Don't mix force fields. See 
http://oldwiki.gromacs.org/index.php/Category:Force_Fields

> The atomtype error is solved  But another
> error again (invalid angle type 0). I'm not sure went wrong. I've check the
> angle types in the ffG53a6, i couldn't see what cause this. Please advice.
> May i know is it possible to use 2 differents forcefield in 1 system since
> the ligand work well with ffgmx and ffG53a6 is good for lipid?

No. You need to develop a topology for both parts based on the same 
force field.

Mark