.. index:: fix store/state

fix store/state command
=======================

Syntax
""""""

.. parsed-literal::

   fix ID group-ID store/state N input1 input2 ... keyword value ...

* ID, group-ID are documented in :doc:`fix <fix>` command
* store/state = style name of this fix command
* N = store atom attributes every N steps, N = 0 for initial store only
* input = one or more atom attributes
.. parsed-literal::

     possible attributes = id, mol, type, mass,
    	                x, y, z, xs, ys, zs, xu, yu, zu, ix, iy, iz,
   		        vx, vy, vz, fx, fy, fz,
                           q, mux, muy, muz,
                           radius, omegax, omegay, omegaz,
                           angmomx, angmomy, angmomz, tqx, tqy, tqz
   			c_ID, c_ID[N], f_ID, f_ID[N], v_name

.. parsed-literal::

         id = atom ID
         mol = molecule ID
         type = atom type
         mass = atom mass
         x,y,z = unscaled atom coordinates
         xs,ys,zs = scaled atom coordinates
         xu,yu,zu = unwrapped atom coordinates
         ix,iy,iz = box image that the atom is in
         vx,vy,vz = atom velocities
         fx,fy,fz = forces on atoms
         q = atom charge
         mux,muy,muz = orientation of dipolar atom
         radius = radius of spherical particle
         omegax,omegay,omegaz = angular velocity of spherical particle
         angmomx,angmomy,angmomz = angular momentum of aspherical particle
         tqx,tqy,tqz = torque on finite-size particles
         c_ID = per-atom vector calculated by a compute with ID
         c_ID[I] = Ith column of per-atom array calculated by a compute with ID
         f_ID = per-atom vector calculated by a fix with ID
         f_ID[I] = Ith column of per-atom array calculated by a fix with ID
         v_name = per-atom vector calculated by an atom-style variable with name

* zero or more keyword/value pairs may be appended
* keyword = *com*
.. parsed-literal::

     *com* value = *yes* or *no*



Examples
""""""""

.. parsed-literal::

   fix 1 all store/state 0 x y z
   fix 1 all store/state 0 xu yu zu com yes
   fix 2 all store/state 1000 vx vy vz

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

Define a fix that stores attributes for each atom in the group at the
time the fix is defined.  If *N* is 0, then the values are never
updated, so this is a way of archiving an atom attribute at a given
time for future use in a calculation or output.  See the discussion of
:ref:`output commands <howto_8>` that take fixes as
inputs.  And see for example, the :doc:`compute reduce <compute_reduce>`, :doc:`fix ave/atom <fix_ave_atom>`, :doc:`fix ave/histo <fix_ave_histo>`, :doc:`fix ave/spatial <fix_ave_spatial>`,
and :doc:`atom-style variable <variable>` commands.

If *N* is not zero, then the attributes will be updated every *N*
steps.

.. warning::

   Actually, only atom attributes specified by keywords
   like *xu* or *vy* are initially stored immediately at the point in
   your input script when the fix is defined.  Attributes specified by a
   compute, fix, or variable are not initially stored until the first run
   following the fix definition begins.  This is because calculating
   those attributes may require quantities that are not defined in
   between runs.

The list of possible attributes is the same as that used by the :doc:`dump custom <dump>` command, which describes their meaning.

If the *com* keyword is set to *yes* then the *xu*, *yu*, and *zu*
inputs store the position of each atom relative to the center-of-mass
of the group of atoms, instead of storing the absolute position.  This
option is used by the :doc:`compute msd <compute_msd>` command.

The requested values are stored in a per-atom vector or array as
discussed below.  Zeroes are stored for atoms not in the specified
group.

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

This fix writes the per-atom values it stores to :doc:`binary restart files <restart>`, so that the values can be restored when a
simulation is restarted.  See the :doc:`read_restart <read_restart>`
command for info on how to re-specify a fix in an input script that
reads a restart file, so that the operation of the fix continues in an
uninterrupted fashion.

None of the :doc:`fix_modify <fix_modify>` options are relevant to this
fix.

If a single input is specified, this fix produces a per-atom vector.
If multiple inputs are specified, a per-atom array is produced where
the number of columns for each atom is the number of inputs.  These
can be accessed by various :ref:`output commands <howto_8>`.  The per-atom values be
accessed on any timestep.

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
""""""""""""
 none

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

:doc:`dump custom <dump>`, :doc:`compute property/atom <compute_property_atom>`, :doc:`variable <variable>`

Default
"""""""

The option default is com = no.


.. _liws: http://www.cfdem.com
.. _ld: Manual.html
.. _lc: Section_commands.html#comm