2006-09-22 00:22:34 +08:00
|
|
|
<HTML>
|
2010-05-07 23:11:21 +08:00
|
|
|
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Page</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
|
2006-09-22 00:22:34 +08:00
|
|
|
</CENTER>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<HR>
|
|
|
|
|
|
|
|
|
|
<H3>min_style command
|
|
|
|
|
</H3>
|
|
|
|
|
<P><B>Syntax:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<PRE>min_style style
|
|
|
|
|
</PRE>
|
2010-10-01 05:22:06 +08:00
|
|
|
<UL><LI>style = <I>cg</I> or <I>hftn</I> or <I>sd</I> or <I>quickmin</I> or <I>fire</I>
|
2006-09-22 00:22:34 +08:00
|
|
|
</UL>
|
|
|
|
|
<P><B>Examples:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<PRE>min_style cg
|
2010-10-01 05:22:06 +08:00
|
|
|
min_style fire
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
|
|
|
|
<P><B>Description:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P>Choose a minimization algorithm to use when a <A HREF = "minimize.html">minimize</A>
|
|
|
|
|
command is performed.
|
|
|
|
|
</P>
|
2010-06-04 08:19:53 +08:00
|
|
|
<P>Style <I>cg</I> is the Polak-Ribiere version of the conjugate gradient (CG)
|
|
|
|
|
algorithm. At each iteration the force gradient is combined with the
|
|
|
|
|
previous iteration information to compute a new search direction
|
|
|
|
|
perpendicular (conjugate) to the previous search direction. The PR
|
|
|
|
|
variant affects how the direction is chosen and how the CG method is
|
|
|
|
|
restarted when it ceases to make progress. The PR variant is thought
|
2010-10-01 05:22:06 +08:00
|
|
|
to be the most effective CG choice for most problems.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2009-09-29 22:10:23 +08:00
|
|
|
<P>Style <I>hftn</I> is a Hessian-free truncated Newton algorithm. At each
|
|
|
|
|
iteration a quadratic model of the energy potential is solved by a
|
|
|
|
|
conjugate gradient inner iteration. The Hessian (second derivatives)
|
|
|
|
|
of the energy is not formed directly, but approximated in each
|
|
|
|
|
conjugate search direction by a finite difference directional
|
|
|
|
|
derivative. When close to an energy minimum, the algorithm behaves
|
|
|
|
|
like a Newton method and exhibits a quadratic convergence rate to high
|
2010-06-04 08:19:53 +08:00
|
|
|
accuracy. In most cases the behavior of <I>hftn</I> is similar to <I>cg</I>,
|
2010-10-01 05:22:06 +08:00
|
|
|
but it offers an alternative if <I>cg</I> seems to perform poorly. This
|
|
|
|
|
style is not affected by the <A HREF = "min_modify.html">min_modify</A> command.
|
2009-09-29 22:10:23 +08:00
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P>Style <I>sd</I> is a steepest descent algorithm. At each iteration, the
|
2008-04-15 05:37:10 +08:00
|
|
|
search direction is set to the downhill direction corresponding to the
|
2010-06-04 08:19:53 +08:00
|
|
|
force vector (negative gradient of energy). Typically, steepest
|
|
|
|
|
descent will not converge as quickly as CG, but may be more robust in
|
|
|
|
|
some situations.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2010-10-01 05:22:06 +08:00
|
|
|
<P>Style <I>quickmin</I> is a damped dynamics method described in
|
|
|
|
|
<A HREF = "#Sheppard">(Sheppard)</A>, where the damping parameter is related to the
|
|
|
|
|
projection of the velocity vector along the current force vector for
|
2010-10-01 06:30:55 +08:00
|
|
|
each atom. The velocity of each atom is initialized to 0.0 by this
|
|
|
|
|
style, at the beginning of a minimization.
|
2010-10-01 05:22:06 +08:00
|
|
|
</P>
|
|
|
|
|
<P>Style <I>fire</I> is a damped dynamics method described in
|
|
|
|
|
<A HREF = "#Bitzek">(Bitzek)</A>, which is similar to <I>quickmin</I> but adds a variable
|
|
|
|
|
timestep and alters the projection operation to maintain components of
|
2010-10-01 06:30:55 +08:00
|
|
|
the velocity non-parallel to the current force vector. The velocity
|
|
|
|
|
of each atom is initialized to 0.0 by this style, at the beginning of
|
|
|
|
|
a minimization.
|
2010-10-01 05:22:06 +08:00
|
|
|
</P>
|
|
|
|
|
<P>Either the <I>quickmin</I> and <I>fire</I> styles are useful in the context of
|
2010-10-01 06:30:55 +08:00
|
|
|
nudged elastic band (NEB) calculations via the <A HREF = "neb.html">neb</A> command.
|
2010-10-01 05:22:06 +08:00
|
|
|
</P>
|
2014-01-31 04:25:43 +08:00
|
|
|
<P>IMPORTANT NOTE: The damped dynamic minimizers use whatever timestep
|
|
|
|
|
you have defined via the <A HREF = "timestep.html">timestep</A> command. Often they
|
|
|
|
|
will converge more quickly if you use a timestep about 10x larger than
|
|
|
|
|
you would normally use for dynamics simulations.
|
|
|
|
|
</P>
|
2010-10-01 05:22:06 +08:00
|
|
|
<P>IMPORTANT NOTE: The <I>quickmin</I> and <I>fire</I> styles do not yet support
|
|
|
|
|
the use of the <A HREF = "fix_box_relax.html">fix box/relax</A> command or
|
|
|
|
|
minimizations involving the electron radius in <A HREF = "pair_eff.html">eFF</A>
|
|
|
|
|
models.
|
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P><B>Restrictions:</B> none
|
|
|
|
|
</P>
|
|
|
|
|
<P><B>Related commands:</B>
|
|
|
|
|
</P>
|
2010-10-01 05:22:06 +08:00
|
|
|
<P><A HREF = "min_modify.html">min_modify</A>, <A HREF = "minimize.html">minimize</A>, <A HREF = "neb.html">neb</A>
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
|
<P><B>Default:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<PRE>min_style cg
|
|
|
|
|
</PRE>
|
2010-10-01 05:22:06 +08:00
|
|
|
<HR>
|
|
|
|
|
|
|
|
|
|
<A NAME = "Sheppard"></A>
|
|
|
|
|
|
|
|
|
|
<P><B>(Sheppard)</B> Sheppard, Terrell, Henkelman, J Chem Phys, 128, 134106
|
|
|
|
|
(2008). See ref 1 in this paper for original reference to Qmin in
|
|
|
|
|
Jonsson, Mills, Jacobsen.
|
|
|
|
|
</P>
|
|
|
|
|
<A NAME = "Bitzek"></A>
|
|
|
|
|
|
2010-10-01 06:30:55 +08:00
|
|
|
<P><B>(Bitzek)</B> Bitzek, Koskinen, Gahler, Moseler, Gumbsch, Phys Rev Lett,
|
2010-10-01 05:22:06 +08:00
|
|
|
97, 170201 (2006).
|
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
</HTML>
|
