fix doc for fix propel/self to sphinx system

   * :doc:`precession/spin <fix_precession_spin>`

   * :doc:`press/berendsen <fix_press_berendsen>`

   * :doc:`print <fix_print>`

   * :doc:`propel/self <fix_propel_self>`

   * :doc:`property/atom (k) <fix_property_atom>`

   * :doc:`python/invoke <fix_python_invoke>`

   * :doc:`python/move <fix_python_move>`

   * :doc:`wall/region/ees <fix_wall_ees>`

   * :doc:`wall/srd <fix_wall_srd>`

   *

   *

.. index:: fix propel/self

fix propel/self command

=======================

Syntax

""""""

fix ID group-ID propel/self mode magnitude keyword values ...

* ID, group-ID are documented in :doc:`fix <fix>` command

* propel/self = style name of this fix command

* mode = velocity or quaternion

* magnitude = magnitude of the active force

* one or more keyword/value pairs may be appended to args

* keyword = *types*

  *types* values = one or more atom types

Examples

""""""""

.. parsed-literal::

   fix active_group all propel/self velocity 1.0

   fix constant_velocity all viscous 1.0

   fix active_group all propel/self quaternion 1.0

   fix active all propel/self quaternion 1.0 types 1 2 4

Description

"""""""""""

Adds a force of a constant magnitude to each atom in the group. The nature in

which the force is added depends on the mode.

For mode = velocity, the active force acts along the velocity vector of each atom. This can

be interpreted as a velocity-dependent friction, such as proposed by :ref:`(Erdmann) <Erdmann>`.

For mode = quaternion the force is along the axis obtained by rotating the x-axis along the

atom's quaternion. In other words, the force is along the x-axis in the atom's body

frame. This mode requires all atoms in the group to have a quaternion, so atom\_style should

either be ellipsoid or body.  In combination with Langevin thermostat for translation and

rotation in the overdamped regime, the quaternion mode corresponds to the active Brownian

particle model introduced by :ref:`(Henkes) <Henkes>`, :ref:`(Bialke) <Bialke>` and :ref:`(Fily) <Fily>`.

By default, this fix is applied to all atoms in the group. You can override this

behavior by specifying the atom types the fix should work on through the *types*

keyword.

----------

**Restart, fix\_modify, output, run start/stop, minimize info:**

No information about this fix is written to :doc:`binary restart files <restart>`.

This fix is not imposed  during minimization.

Restrictions

""""""""""""

In quaternion mode, this fix makes use of per-atom quaternions to take into account the fact

that the orientation can rotate and hence the direction of the active force can

change. Therefore, the quaternion mode of this fix only works with atom\_styles that have a

quaternion.

Related commands

""""""""""""""""

:doc:`fix setforce <fix_setforce>`, :doc:`fix addforce <fix_addforce>`

.. _Erdmann:

**(Erdmann)** U. Erdmanna , W. Ebeling, L. Schimansky-Geier, and F. Schweitzer,

Eur. Phys. J. B 15, 105-113, 2000.

.. _Henkes:

**(Henkes)** Henkes, S, Fily, Y., and Marchetti, M. C. Phys. Rev. E, 84, 040301(R), 2011.

.. _Bialke:

**(Bialke)** J. Bialké, T. Speck, and H Löwen, Phys. Rev. Lett. 108, 168301, 2012.

.. _Fily:

**(Fily)** Y. Fily and M.C. Marchetti, Phys. Rev. Lett. 108, 235702, 2012.

**Default:** types

.. _lws: http://lammps.sandia.gov

.. _ld: Manual.html

.. _lc: Commands_all.html

Eur. Phys. J. B 15, 105-113, 2000.

:link(Henkes)

[(Henkes)] Henkes, S, Fily, Y., and Marchetti, M. C. Phys. Rev. E, 84, 040301(R), 2011

[(Henkes)] Henkes, S, Fily, Y., and Marchetti, M. C. Phys. Rev. E, 84, 040301(R), 2011.

:link(Bialke)

[(Bialke)] J. Bialké, T. Speck, and H Löwen, Phys. Rev. Lett. 108, 168301, 2012.