.. index:: fix enforce2d

fix enforce2d command
=====================

Syntax
""""""

.. parsed-literal::

   fix ID group-ID enforce2d

* ID, group-ID are documented in :doc:`fix <fix>` command
* enforce2d = style name of this fix command

Examples
""""""""

.. parsed-literal::

   fix 5 all enforce2d

Description
"""""""""""

Zero out the z-dimension velocity and force on each atom in the group.
This is useful when running a 2d simulation to insure that atoms do
not move from their initial z coordinate.


----------


Styles with a suffix are functionally the same as the corresponding
style without the suffix.  They have been optimized to run faster,
depending on your available hardware, as discussed in
:doc:`Section_accelerate <Section_accelerate>` of the manual.  The
accelerated styles take the same arguments and should produce the same
results, except for round-off and precision issues.

These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
USER-OMP and OPT packages, respectively.  They are only enabled if
LAMMPS was built with those packages.  See the :ref:`Making LAMMPS <start_3>` section for more info.

You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
use the :doc:`suffix <suffix>` command in your input script.

See :doc:`Section_accelerate <Section_accelerate>` of the manual for
more instructions on how to use the accelerated styles effectively.


----------


Restart, fix_modify, output, run start/stop, minimize info
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

No information about this fix is written to :doc:`binary restart files <restart>`.  None of the :doc:`fix_modify <fix_modify>` options
are relevant to this fix.  No global or per-atom quantities are stored
by this fix for access by various :ref:`output commands <howto_15>`.  No parameter of this fix can
be used with the *start/stop* keywords of the :doc:`run <run>` command.

The forces due to this fix are imposed during an energy minimization,
invoked by the :doc:`minimize <minimize>` command.

Restrictions
""""""""""""
 none

**Related commands:** none

**Default:** none


.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm