[gmx-users] energy minimization

[Madhuri Agashe]

While doing energy minimization, what is the effect of specifying nsteps?
Does nsteps decide the number of steps for which minimization will run?

 From the manual I thought that this would be decided by emtol.

But for a minimization run that I ran, I first did not specify nsteps.
This is what I saw in the log:
Steepest Descents:
   Tolerance         =  1.00000e+03
   Number of steps   =            0

Stepsize too small (7.31232e-07 nm)Converged to machine precision,
but not to the requested precision (1000)

writing lowest energy coordinates.

Steepest Descents did not converge in 0 steps
  Potential Energy  =  6.86585e+10
Maximum force:  3.51153e+05

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I then ran the same minimization again this time specifying nsteps=5000
This is the output I got:

Steepest Descents:
   Tolerance         =  1.00000e+03
   Number of steps   =         5000

Stepsize too small (7.31232e-07 nm)Converged to machine precision,
but not to the requested precision (1000)

writing lowest energy coordinates.


Steepest Descents did not converge in 40 steps
  Potential Energy  =  6.86585e+10
Maximum force:  3.51153e+05


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The potential energy and the maximum force at the end of both the run seems
to be the same. Then what is the significance of 40 steps and 0 steps?


This is a little confusing!

Madhuri Agashe