git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@14950 f3b2605a-c512-4ea7-a41b-209d697bcdaa

doc/html/_sources/min_style.txt

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+.. index:: min_style
+
+min_style command
+=================
+
+Syntax
+""""""
+
+.. parsed-literal::
+
+   min_style style
+
+* style = *cg* or *hftn* or *sd* or *quickmin* or *fire*
+
+Examples
+""""""""
+
+.. parsed-literal::
+
+   min_style cg
+   min_style fire
+
+Description
+"""""""""""
+
+Choose a minimization algorithm to use when a :doc:`minimize <minimize>`
+command is performed.
+
+Style *cg* 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
+to be the most effective CG choice for most problems.
+
+Style *hftn* 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
+accuracy.  In most cases the behavior of *hftn* is similar to *cg*\ ,
+but it offers an alternative if *cg* seems to perform poorly.  This
+style is not affected by the :doc:`min_modify <min_modify>` command.
+
+Style *sd* is a steepest descent algorithm.  At each iteration, the
+search direction is set to the downhill direction corresponding to the
+force vector (negative gradient of energy).  Typically, steepest
+descent will not converge as quickly as CG, but may be more robust in
+some situations.
+
+Style *quickmin* is a damped dynamics method described in
+:ref:`(Sheppard) <Sheppard>`, where the damping parameter is related to the
+projection of the velocity vector along the current force vector for
+each atom.  The velocity of each atom is initialized to 0.0 by this
+style, at the beginning of a minimization.
+
+Style *fire* is a damped dynamics method described in
+:ref:`(Bitzek) <Bitzek>`, which is similar to *quickmin* but adds a variable
+timestep and alters the projection operation to maintain components of
+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.
+
+Either the *quickmin* and *fire* styles are useful in the context of
+nudged elastic band (NEB) calculations via the :doc:`neb <neb>` command.
+
+.. note::
+
+   The damped dynamic minimizers use whatever timestep you have
+   defined via the :doc:`timestep <timestep>` command.  Often they will
+   converge more quickly if you use a timestep about 10x larger than you
+   would normally use for dynamics simulations.
+
+.. note::
+
+   The *quickmin* and *fire* styles do not yet support the use of
+   the :doc:`fix box/relax <fix_box_relax>` command or minimizations
+   involving the electron radius in :doc:`eFF <pair_eff>` models.
+
+Restrictions
+""""""""""""
+ none
+
+Related commands
+""""""""""""""""
+
+:doc:`min_modify <min_modify>`, :doc:`minimize <minimize>`, :doc:`neb <neb>`
+
+Default
+"""""""
+
+.. parsed-literal::
+
+   min_style cg
+
+
+----------
+
+
+.. _Sheppard:
+
+
+
+**(Sheppard)** Sheppard, Terrell, Henkelman, J Chem Phys, 128, 134106
+(2008).  See ref 1 in this paper for original reference to Qmin in
+Jonsson, Mills, Jacobsen.
+
+.. _Bitzek:
+
+
+
+**(Bitzek)** Bitzek, Koskinen, Gahler, Moseler, Gumbsch, Phys Rev Lett,
+97, 170201 (2006).
+
+
+.. _lws: http://lammps.sandia.gov
+.. _ld: Manual.html
+.. _lc: Section_commands.html#comm