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compute_ackland_atom.txt
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.. index:: compute ackland/atom
compute ackland/atom command
============================
Syntax
""""""
.. parsed-literal::
compute ID group-ID ackland/atom
* ID, group-ID are documented in :doc:`compute <compute>` command
* ackland/atom = style name of this compute command
Examples
""""""""
.. parsed-literal::
compute 1 all ackland/atom
Description
"""""""""""
Defines a computation that calculates the local lattice structure
according to the formulation given in :ref:`(Ackland) <Ackland>`.
In contrast to the :doc:`centro-symmetry parameter <compute_centro_atom>` this method is stable against
temperature boost, because it is based not on the distance between
particles but the angles. Therefore statistical fluctuations are
averaged out a little more. A comparison with the Common Neighbor
Analysis metric is made in the paper.
The result is a number which is mapped to the following different
lattice structures:
* 0 = UNKNOWN
* 1 = BCC
* 2 = FCC
* 3 = HCP
* 4 = ICO
The neighbor list needed to compute this quantity is constructed each
time the calculation is performed (i.e. each time a snapshot of atoms
is dumped). Thus it can be inefficient to compute/dump this quantity
too frequently or to have multiple compute/dump commands, each of
which computes this quantity.-
**Output info:**
This compute calculates a per-atom vector, which can be accessed by
any command that uses per-atom values from a compute as input. See
:ref:`Section_howto 15 <howto_15>` for an overview of
LAMMPS output options.
Restrictions
""""""""""""
This compute is part of the USER-MISC package. It is only enabled if
LAMMPS was built with that package. See the :ref:`Making LAMMPS <start_3>` section for more info.
The per-atom vector values will be unitless since they are the
integers defined above.
Related commands
""""""""""""""""
:doc:`compute centro/atom <compute_centro_atom>`
**Default:** none
----------
.. _Ackland:
**(Ackland)** Ackland, Jones, Phys Rev B, 73, 054104 (2006).
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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