How to fix error of Incorrect number of parameters - found 1, expected 2 or 4 for Bond

User discussions
1

GROMACS version:2020
GROMACS modification: yes
Here post your question How to fix the error “Incorrect number of parameters - found 1, expected 2 or 4 for Bond (after the function type).”
Dear gromacs users
I am doing a protein-ligand simulation for which I build forcefield for ligand as mentioned in gromacs manual. When I do grompp as follows:-
gmx grompp -f ions.mdp -c 203F-Lbsolv.gro -p topol.top -o ions.tpr -maxwarn 1
I get following error message
ERROR 1 [file topol_LIG_chain_A2.itp, line 205]:
Incorrect number of parameters - found 1, expected 2 or 4 for Bond (after
the function type).
I checked the line 205 of the topol_LIG_chain_A2.top (46.0 KB) above-mentioned file, which is as below:-

[ bonds ]
; ai aj funct c0 c1 c2 c3
1 12 1 1
1 22 1 1
1 26 1 1
1 38 1 1
2 10 1 1
2 21 1 1
2 33 1 1
2 57 1 1
3 11 1 1
How should I solve this error?
Please find the file attached.
Thanks in advance.
Sadaf

2

The proper format is:

ai aj function kb b0

or

ai aj function

So when grompp parses your topology, it finds the two atom numbers, the function (1), then a force constant of 1, and no b0 value. Either you need to provide complete parameters (kb and b0) or none at all (in which case they are read from ffbonded.itp).

3

thank you justin. It worked with format “ai aj function”
Regards