[gmx-users] Energy minimizations with gmx3.2

[Marc Vogt]

No I had not been able to find any solutions in the archive, but I tried 
just now and although the minimization ran for 252 steps in 3.2.1
with define = -DFLEXIBLE instead of 37 steps for define = -DFLEX_SPC,
it still failed.:

With 3.2.1 and define = -DFLEXIBLE and contraints=none
--------------------------------------------------------------
Step=  251, Dmax= 1.7e-06 nm, Epot= -1.79236e+05 Fmax= 2.01564e+03, atom= 68
Stepsize too small, or no change in energy.
Converged to machine precision,
but not to the requested precision Fmax < 1000

Double precision normally gives you higher accuracy.

writing lowest energy coordinates.

Back Off! I just backed up test.gro to ./#test.gro.2#

Steepest Descents converged to machine precision in 252 steps,
but did not reach the requested Fmax < 1000.
Potential Energy  = -1.7923609e+05
Maximum force     =  2.0180422e+03 on atom 68
Norm of force     =  9.6549727e+03


With 3.1.4 and define=DFLEX_SPC
-----------------------------------------------------------------
Step=  109, Dmax= 6.4e-03 nm, Epot= -1.75318e+05 Fmax= 9.59784e+02, atom= 6814

writing lowest energy coordinates.

Back Off! I just backed up mintraj.trr to ./#mintraj.trr.2#

Back Off! I just backed up test.gro to ./#test.gro.3#

Steepest Descents converged to 1000 in 110 steps
  Potential Energy  = -1.75318e+05
Maximum force:  9.59784e+02




-----------------------------------------------------------------
-----------------------------------------------------------------

Other than the define= field, the mdp is the same

title               =  testww
cpp                 =  /lib/cpp
define              =  -DFLEX_SPC
constraints         =  none
integrator          =  steep
dt                  =  0.002    ; ps !
nsteps              =  1000
nstlist             =  10
ns_type             =  grid
rlist               =  1.0
rcoulomb            =  1.0
rvdw                =  1.0
;
;       Energy minimizing stuff
;
emtol               =  1000.0
emstep              =  0.01
epsilon_r           =  1


thanks,
Marc


> 
> On Mon, 2004-05-17 at 15:05, Marc Vogt wrote:
> > I had the same problem using DFLEX_SPC.  Never could resolve it
> > along with a restart problem.  Both in 3.2.1. 
> > Consequently, I'm still using 3.1.4.
> Have you tried
> define = -DFLEXIBLE
> constraints = none
> > 
> > Marc
> > 
> > > 
> > > Which water model you use?
> > > I encountered the same problem when using TIP4P.
> > > 
> > > Tanos wrote:
> > > 
> > > >    Hi folks,
> > > >    Since I started to use gmx 3.2 my energy minimizations stopped to 
> > > > converge to emtol. All of them have converged to the machine precision 
> > > > !!!!!! Is that happening to someone else ??? If ss, does someone knows 
> > > > the reason ?????
> > > >    Thanks in advance.
> > > >    Tanos C. C. Franca - IME
> > > >    Rio de Janeiro - RJ
> > > >    Brazil
> > > >
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> ________________________________________________________________________
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