[gmx-users] question about Polak Ribiere conjugate gradient

[Hua Wong]

I am doing a minimization using the brand new GROMACS 3.2. It works fine on a system that previously lead to error with GROMACS 3.1.

I am working on a protein minimised under NAMD and wanted to minimise it further using GROMACS to correct some omega torsion problems. All seems to be fine, only I obtain a warning :

Stepsize too small, or no change in energy.
Converged to machine precision,
but not to the requested precision Fmax < 1e-06

I am using CG with GROMACS compiled in double precision. 

Here is the .mdp file I use.
##################################
title                    = GMXminiomega
cpp                      = /lib/cpp
include                  = -I../top
define                   = -DFLEXIBLE
integrator               = cg
emtol                    = 0.000001
emstep                   = 0.01
nstcgsteep               = 100
nsteps                   = 3000
nstxout                  = 50
xtc_grps                 = Protein
energygrps               = Protein
nstlist                  = 5
ns_type                  = grid
rlist                    = 1.
vdwtype                  = cut-off
coulombtype              = cut-off
rcoulomb                 = 1.
rvdw                     = 1.

Is there anything I've forgotten ? 

Thanks