83 lines
2.3 KiB
ReStructuredText
83 lines
2.3 KiB
ReStructuredText
.. index:: compute basal/atom
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compute basal/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 basal/atom
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* basal/atom = style name of this compute command
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Examples
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""""""""
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.. code-block:: LAMMPS
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compute 1 all basal/atom
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Description
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"""""""""""
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Defines a computation that calculates the hexagonal close-packed "c"
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lattice vector for each atom in the group. It does this by
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calculating the normal unit vector to the basal plane for each atom.
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The results enable efficient identification and characterization of
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twins and grains in hexagonal close-packed structures.
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The output of the compute is thus the 3 components of a unit vector
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associated with each atom. The components are set to 0.0 for
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atoms not in the group.
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Details of the calculation are given in :ref:`(Barrett) <Barrett>`.
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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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An example input script that uses this compute is provided
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in examples/PACKAGES/basal.
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Output info
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"""""""""""
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This compute calculates a per-atom array with 3 columns, which can be
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accessed by indices 1-3 by any command that uses per-atom values from
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a compute as input. See the :doc:`Howto output <Howto_output>` doc page
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for an overview of LAMMPS output options.
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The per-atom vector values are unitless since the 3 columns represent
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components of a unit vector.
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Restrictions
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""""""""""""
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This compute is part of the EXTRA-COMPUTE package. It is only enabled if
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LAMMPS was built with that package. See the :doc:`Build package <Build_package>` page for more info.
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The output of this compute will be meaningless unless the atoms are on
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(or near) hcp lattice sites, since the calculation assumes a
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well-defined basal plane.
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Related commands
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""""""""""""""""
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:doc:`compute centro/atom <compute_centro_atom>`, :doc:`compute ackland/atom <compute_ackland_atom>`
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Default
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"""""""
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none
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----------
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.. _Barrett:
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**(Barrett)** Barrett, Tschopp, El Kadiri, Scripta Mat. 66, p.666 (2012).
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