[gmx-users] largest charge group

[Maryam Sadeghi]

Dear All,

I have created a coarse-grain (cg) structure of a polymer containing 49
beads (the atomistic structure contains 193 atoms), each beads has a zero
charge.
I have created the .itp file manually, defining the atom types and the
bonds  and angles (no dihedrals in my model). When I used GROMAC's grompp
command, I get the following error:

gmx grompp -f em.mdp -c cg_PCL_box.gro -p topol.top -o em.tpr -maxwarn 1

Fatal error:
The largest charge group contains 49 atoms. The maximum is 32.
For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors

Could anyone suggest how I can fix this problem? I will need to do
simulations on longer chains as well.

Thank you
Maryam