.. index:: fix sph

fix sph command
================

Syntax
""""""

.. parsed-literal::

   fix ID group-ID sph

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

Examples
""""""""

.. code-block:: LAMMPS

   fix 1 all sph

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

Perform time integration to update position, velocity, internal energy
and local density for atoms in the group each timestep. This fix is
needed to time-integrate SPH systems where particles carry internal
variables such as internal energy.  SPH stands for Smoothed Particle
Hydrodynamics.

See `this PDF guide <USER/sph/SPH_LAMMPS_userguide.pdf>`_ to using SPH in
LAMMPS.

**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 :doc:`output commands <Howto_output>`.
No parameter of this fix can be used with the *start/stop* keywords of
the :doc:`run <run>` command.  This fix is not invoked during :doc:`energy minimization <minimize>`.

Restrictions
""""""""""""

This fix is part of the USER-SPH package.  It is only enabled if
LAMMPS was built with that package.  See the :doc:`Build package <Build_package>` doc page for more info.

Related commands
""""""""""""""""

:doc:`fix sph/stationary <fix_sph_stationary>`

**Default:** none
