Incorrect number of parameters for proper dihedrals

User discussions
1

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 dopc_pip2.top -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 - insane.py 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:

[dihedrals]
; 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,

Sweta.

2

Hi,
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

Alessandra

3

Ok Thanks, I will try to get the multiplicity.