[gmx-users] Incorrect number of parameters in improper dihedral

Debadutta Prusty debaduttaprusty1.2015 at u.northwestern.edu
Tue Jul 17 02:35:13 CEST 2018

Hi everyone,

I ran an energy minimization run on a single polymer chain. On running the
gmx grompp  -f  .mdp ...., I get the following error message:
"ERROR 1 [file topol.top, line 1486]:
 Incorrect number of parameters - found 3, expected 2 or 4 for Improper

The corresponding line(line 1486) in the topology file is:
;  ai    aj    ak    al funct            c0            c1
c2            c3
    8     7     1    15     2    improper_X_CA_Y_Z

The entry containing the definition of this forcefield in the ffbonded.itp
(I am using opls all atom force field) file is
; X-CA-Y-Z improper torsion. CA is any ring carbon in pyridine
#define improper_X_CA_Y_Z       180.0     10.460     2

The topology file for the above polymer was generated by using the command
pdb2gmx(it operated on the pdb file of the polymer chain).

Please help me out.

More information about the gromacs.org_gmx-users mailing list