"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

:line

min_modify command :h3

[Syntax:]

min_modify keyword values ... :pre

one or more keyword/value pairs may be listed :ulb,l
keyword = {dmax} or {line}
  {dmax} value = max
    max = maximum distance for line search to move (distance units)
  {line} value = {backtrack} or {quadratic}
    backtrack,quadratic = style of linesearch to use :pre
:ule

[Examples:]

min_modify dmax 0.2 :pre

[Description:]

This command sets parameters that affect the energy minimization
algorithms.  The various settings may affect the convergence rate and
overall number of force evaluations required by a minimization, so
users can experiment with these parameters to tune their
minimizations.

The minimization algorithms have an outer iteration (conjugate
gradient or steepest descent) and an inner iteration which is steps
along a one-dimensional line search in a particular search direction.
The {dmax} parameter is how far any atom can move in a single line
search in any dimension (x, y, or z).  Thus a value of 0.1 in real
"units"_units.html means no atom will move further than 0.1 Angstroms
in a single outer iteration.  This prevents highly overlapped atoms
from being moved long distances (e.g. through another atom) due to
large forces.

The choice of line search algorithm can be selected via the {line}
keyword.  The default backtracking search is very robust and should
always find a local energy minimum.  However, it will "converge" when
it can no longer reduce the energy of the system.  Individual atom
forces may still be larger than desired at this point, because the
energy change is measured as the difference of two large values
(energy before and energy after) and that difference may be smaller
than machine epsilon even if atoms could move in the gradient
direction to reduce forces further.

By contast, the {quadratic} line search algorithm is often able to
reduce forces closer to 0.0.  It may also be more efficient than the
backtracking algorithm by requiring fewer energy/force evaluations.
However, it may not be as robust for some problems.

[Restrictions:] none

[Related commands:]

"min_style"_min_style.html, "minimize"_minimize.html

[Default:]

The option defaults are dmax = 0.1 and line = backtrack.
