.. index:: compute property/atom

compute property/atom command
=============================

Syntax
""""""

.. parsed-literal::

   compute ID group-ID property/atom general_keyword general_values input1 input2 ...

* ID, group-ID are documented in :doc:`compute <compute>` command
* property/atom = style name of this compute command
* general_keywords general_values are documented in `compute <compute.html">`_
* 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, mu,
                           radius, diameter, omegax, omegay, omegaz,
   			angmomx, angmomy, angmomz,
   			shapex,shapey, shapez,
   		        quatw, quati, quatj, quatk, tqx, tqy, tqz,
   			end1x, end1y, end1z, end2x, end2y, end2z,
   			corner1x, corner1y, corner1z,
   			corner2x, corner2y, corner2z,
   			corner3x, corner3y, corner3z,
                           i_name, d_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 dipole moment of atom
         mu = magnitude of dipole moment of atom
         radius,diameter = radius,diameter of spherical particle
         omegax,omegay,omegaz = angular velocity of spherical particle
         angmomx,angmomy,angmomz = angular momentum of aspherical particle
         shapex,shapey,shapez = 3 diameters of aspherical particle
         quatw,quati,quatj,quatk = quaternion components for aspherical or body particles
         tqx,tqy,tqz = torque on finite-size particles
         end12x, end12y, end12z = end points of line segment
         coner123x, corner123y, corner123z = corner points of triangle
         i_name = custom integer vector with name
         d_name = custom integer vector with name



Examples
""""""""

.. parsed-literal::

   compute 1 all property/atom xs vx fx mux
   compute 2 all property/atom type
   compute 1 all property/atom ix iy iz

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

Define a computation that simply stores atom attributes for each atom
in the group.  This is useful so that the values can be used by other
:ref:`output commands <howto_8>` that take computes as
inputs.  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.

The list of possible attributes is the same as that used by the :doc:`dump custom <dump>` command, which describes their meaning, with some
additional quantities that are only defined for certain :doc:`atom styles <atom_style>`.  Basically, this list gives your input script
access to any per-atom quantity stored by LIGGGHTS(R)-PUBLIC.

The values are stored in a per-atom vector or array as discussed
below.  Zeroes are stored for atoms not in the specified group or for
quantities that are not defined for a particular particle in the group
(e.g. *shapex* if the particle is not an ellipsoid).

The additional quantities only accessible via this command, and not
directly via the :doc:`dump custom <dump>` command, are as follows.

*Shapex*, *shapey*, and *shapez* are defined for ellipsoidal particles
and define the 3d shape of each particle.

*Quatw*, *quati*, *quatj*, and *quatk* are defined for ellipsoidal
particles and body particles and store the 4-vector quaternion
representing the orientation of each particle.  See the :doc:`set <set>`
command for an explanation of the quaternion vector.

*End1x*, *end1y*, *end1z*, *end2x*, *end2y*, *end2z*, are defined for
line segment particles and define the end points of each line segment.

*Corner1x*, *corner1y*, *corner1z*, *corner2x*, *corner2y*,
*corner2z*, *corner3x*, *corner3y*, *corner3z*, are defined for
triangular particles and define the corner points of each triangle.

The *i_name* and *d_name* attributes refer to custom integer and
floating-point properties that have been added to each atom via the
:doc:`fix property/atom <fix_property_atom>` command.  When that command
is used specific names are given to each attribute which are what is
specified as the "name" portion of *i_name* or *d_name*.

Output info
"""""""""""

This compute calculates a per-atom vector or per-atom array depending
on the number of input values.  If a single input is specified, a
per-atom vector is produced.  If two or more inputs are specified, a
per-atom array is produced where the number of columns = the number of
inputs.  The vector or array can be accessed by any command that uses
per-atom values from a compute as input.  See :ref:`this section <howto_8>` for an overview of LIGGGHTS(R)-PUBLIC output
options.

The vector or array values will be in whatever :doc:`units <units>` the
corresponding attribute is in, e.g. velocity units for vx, charge
units for q, etc.

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

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

:doc:`dump custom <dump>`, :doc:`compute reduce <compute_reduce>`, :doc:`fix ave/atom <fix_ave_atom>`, :doc:`fix ave/spatial <fix_ave_spatial>`,
:doc:`fix property/atom <fix_property_atom>`

**Default:** none


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