[gmx-users] error during nvt equilibration

[Shine A]

Sir,

   I am studying the dynamics of membrane proteins using KALP-15 in DPPC.
Now doing nvt equilibration and created index.ndx by using make_ndx. During
this step I selected "16/14" and "1/13".The next step (grompp -f nvt.mdp -c
em.gro -p topol.top -n index.ndx -o nvt.tpr) getting error like this

 Fatal error:
Group SOL_CL not found in indexfile.
Maybe you have non-default goups in your .mdp file, while not using the
'-n' option of grompp.
In that case use the '-n' option.
 why this error? Can you give a solution to overcome it?