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