mirror of https://github.com/lammps/lammps.git
71 lines
2.0 KiB
Plaintext
71 lines
2.0 KiB
Plaintext
.. index:: fix drag
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fix drag 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 drag x y z fmag delta
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* ID, group-ID are documented in :doc:`fix <fix>` command
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* drag = style name of this fix command
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* x,y,z = coord to drag atoms towards
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* fmag = magnitude of force to apply to each atom (force units)
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* delta = cutoff distance inside of which force is not applied (distance units)
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Examples
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""""""""
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.. parsed-literal::
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fix center small-molecule drag 0.0 10.0 0.0 5.0 2.0
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Description
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"""""""""""
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Apply a force to each atom in a group to drag it towards the point
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(x,y,z). The magnitude of the force is specified by fmag. If an atom
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is closer than a distance delta to the point, then the force is not
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applied.
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Any of the x,y,z values can be specified as NULL which means do not
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include that dimension in the distance calculation or force
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application.
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This command can be used to steer one or more atoms to a new location
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in the simulation.
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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 computes a global 3-vector of forces, which can be accessed
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by various :ref:`output commands <howto_15>`. This is the
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total force on the group of atoms by the drag force. The vector
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values calculated by this fix are "extensive".
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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 spring <fix_spring>`, :doc:`fix spring/self <fix_spring_self>`,
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:doc:`fix spring/rg <fix_spring_rg>`, :doc:`fix smd <fix_smd>`
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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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