forked from lijiext/lammps
81 lines
2.7 KiB
Plaintext
81 lines
2.7 KiB
Plaintext
.. index:: fix store/force
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fix store/force command
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=======================
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Syntax
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""""""
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.. parsed-literal::
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fix ID group-ID store/force
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* ID, group-ID are documented in :doc:`fix <fix>` command
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* store/force = style name of this fix command
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Examples
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""""""""
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.. parsed-literal::
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fix 1 all store/force
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Description
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"""""""""""
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Store the forces on atoms in the group at the point during each
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timestep when the fix is invoked, as described below. This is useful
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for storing forces before constraints or other boundary conditions are
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computed which modify the forces, so that unmodified forces can be
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:doc:`written to a dump file <dump>` or accessed by other :ref:`output commands <howto_15>` that use per-atom quantities.
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This fix is invoked at the point in the velocity-Verlet timestepping
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immediately after :doc:`pair <pair_style>`, :doc:`bond <bond_style>`,
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:doc:`angle <angle_style>`, :doc:`dihedral <dihedral_style>`,
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:doc:`improper <improper_style>`, and :doc:`long-range <kspace_style>`
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forces have been calculated. It is the point in the timestep when
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various fixes that compute constraint forces are calculated and
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potentially modify the force on each atom. Examples of such fixes are
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:doc:`fix shake <fix_shake>`, :doc:`fix wall <fix_wall>`, and :doc:`fix indent <fix_indent>`.
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.. note::
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The order in which various fixes are applied which operate at
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the same point during the timestep, is the same as the order they are
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specified in the input script. Thus normally, if you want to store
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per-atom forces due to force field interactions, before constraints
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are applied, you should list this fix first within that set of fixes,
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i.e. before other fixes that apply constraints. However, if you wish
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to include certain constraints (e.g. fix shake) in the stored force,
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then it could be specified after some fixes and before others.
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Restart, fix_modify, output, run start/stop, minimize info
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""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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No information about this fix is written to :doc:`binary restart files <restart>`. None of the :doc:`fix_modify <fix_modify>` options
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are relevant to this fix.
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This fix produces a per-atom array which can be accessed by various
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:ref:`output commands <howto_15>`. The number of columns
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for each atom is 3, and the columns store the x,y,z forces on each
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atom. The per-atom values be accessed on any timestep.
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No parameter of this fix can be used with the *start/stop* keywords of
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the :doc:`run <run>` command. This fix is not invoked during :doc:`energy minimization <minimize>`.
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Restrictions
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""""""""""""
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none
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Related commands
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""""""""""""""""
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:doc:`fix store_state <fix_store_state>`
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**Default:** none
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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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