On 7/5/12 10:52 AM, reising...@rostlab.informatik.tu-muenchen.de wrote:
Hi everybody,
I want to minimize the energy of my structure.
I use the following mdp file:

define                  = -DPOSRES
integrator              = steep
emtol           = 10
nsteps          = 5000
nstenergy               = 1
energygrps              = System
coulombtype             = PME
rcoulomb                = 0.9
rvdw                    = 0.9
rlist           = 0.9
fourierspacing  = 0.12
pme_order               = 4
ewald_rtol              = 1e-5
pbc                     = xyz

But it nevers runs till the end. It allways stops before the end and I get
no pdb file. When I use nsteps = 2000 there is no problem and I receive a
pdb file but it says that there were not enough steps to get under a
specific force value.

My question is: is there a possibility to make the minimization run
longer? Can I set a parameter that makes it run longer?


Set nsteps to either a very high value or to -1 (which says run infinitely long). Note that several factors are working against you here, including the use of position restraints. These disfavor the motion of whatever the restrained atoms are, which can impede energy minimization. Also, assuming you're using single-precision Gromacs, an emtol of 10 is very low and unlikely to be achievable, especially using a single run of steepest descent EM.

-Justin

--
========================================

Justin A. Lemkul, Ph.D.
Research Scientist
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

========================================


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