[gmx-users] CGennFF in gromacs

[Golshan Hejazi]

Hello everyone,

I want to use CGennFF force field in GROMACS. I downloaded the Cgenffbon.itp and  Cgenffnb.itp files and I put them in charmm36.ff directory. 

- I replaced the lines in the forcefield.itp to #include "Cgenffbon.itp"  and #include "Cgenffnb.itp" 
- I modified the rtp file and I inserted the corresponding atom, bond, dihedral terms as in charmm rtf file for paracetamol in the rtp file in gromacs 
- I inserted the new atomtypes at the end of the atomtype.atp file ... I took the atom types from prm file of charmm
- I introduced the new residue name to the residuetype file
- with pdb2gmx ... I could generate the topol.top file without any error

However, when I am using grompp, it give me the following error:

Fatal error:
Atomtype CG331 not found
For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors


I already have this atomtype inside the atomtype file ... and when I was pdb2gmx ... it did not complain ! Can you help me to figure out what is going on?

Thanks
G.