[gmx-users] Facing poblem in enegy minimization step

[Swagata Patra]

Hello evryone,

I am tying to do simulation of a protein-ligand complex. But in energy
minimization step I am facing the following problem:


Stepsize too small, or no change in energy.
Converged to machine precision,
but not to the requested precision Fmax < 1
You might need to increase your constraint accuracy, or turn
off constraints alltogether (set constraints = none in mdp file)

writing lowest energy coordinates.

Steepest Descents converged to machine precision in 37686 steps,
but did not reach the requested Fmax < 1.
Potential Energy  = -1.22228866049133e+06
Maximum force     =  1.60313450715092e+02 on atom 1628
Norm of force     =  1.38085169243203e+00

i prepared the ligand topology file using ATB. There I was getting an
warning like : "This molecule contains non-standard atom types not included
in the standard GROMOS 53A6 and 54A7 forcefield. To use these atom types
the internal GROMACS parameter files must be updated. These can be
downloaded using the link below. So I donloaded the filee and also modify
it in topology file.

Please help me to overcome the problem.
I am attaching the topology file.

-- 
Swagata Patra
M.Tech (Biotech)
JRF
IIT Guwahati