Incorrect number of parameters for proper dihedrals

GROMACS version: 5.1.5
GROMACS modification: No
Here post your question How to fix the error of incorrect number of parameters - found 2, expected 3 or 6 for Proper Dihedral.

Hi all users,
I am doing a lipid bilayer simulation. To build the topology file for the bilayer mixture, I have used martini forcefield and while running the minimization with the command:
gmx_mpi grompp -f minimization.mdp -c dopc_pip2.gro -p -o dopc_pip2_min.tpr

I got the following error:
Fatal error:
Incorrect number of parameters - found 2, expected 3 or 6 for Proper Dih…

I have generated the topology file through a python script - and have included the required itp files.
The topology file is :

#include “martini_v2.2.itp”
#include “martini_v2.0_DOPC_02.itp”
#include “martini_PIP2.itp”
#include “martini_v2.0_solvents.itp”
#include “martini_v2.0_ions.itp”

[ system ]
; name
INSANE! Membrane UpperLeaflet>DOPC:POP2=6.0:4.0 LowerLeaflet>DOPC:POP2=6.0:4.0

[ molecules ]
; name number
DOPC 135
POP2 90
DOPC 135
POP2 90
W 5501
NA+ 61
CL- 61

The Dihedral input part of martini_PIP2.itp file is:

; i j k l funct angle force.c.
3 1 4 7 1 -30.0 5.0
5 1 2 3 1 50 12
6 2 1 3 1 180 100.0

Please suggest me how to solve this error.
Thanks and regards,


in the dihedral definition the multiplicity is missing.
See here has example

See also here proper dihedral (func=1) required 3 parameters

That was also the case for 5.1 version.
Best regards


Ok Thanks, I will try to get the multiplicity.