forked from lijiext/lammps
78 lines
2.6 KiB
Plaintext
78 lines
2.6 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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fix addforce command :h3
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[Syntax:]
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fix ID group-ID addforce fx fy fz keyword value ... :pre
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ID, group-ID are documented in "fix"_fix.html command :ulb,l
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addforce = style name of this fix command :l
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fx,fy,fz = force component values (force units) :l
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zero or more keyword/value pairs may be appended to args :l
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keyword = {region} :l
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{region} value = region-ID
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region-ID = ID of region atoms must be in to have added force :pre
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:ule
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[Examples:]
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fix kick flow addforce 1.0 0.0 0.0 :pre
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[Description:]
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Add fx,fy,fz to the corresponding component of force for each atom in
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the group. This command can be used to give an additional push to
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atoms in a simulation, such as for a simulation of Poiseuille flow in
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a channel.
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If the {region} keyword is used, the atom must also be in the
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specified geometric "region"_region.html in order to have force added
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to it.
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[Restart, fix_modify, output, run start/stop, minimize info:]
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No information about this fix is written to "binary restart
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files"_restart.html.
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The "fix_modify"_fix_modify.html {energy} option is supported by this
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fix to add the potential "energy" inferred by the added force to the
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system's potential energy as part of "thermodynamic
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output"_thermo_style.html. This is a fictitious quantity but is
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needed so that the "minimize"_minimize.html command can include the
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forces added by this fix in a consistent manner. I.e. there is a
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decrease in potential energy when atoms move in the direction of the
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added force.
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This fix computes a scalar and a 3-vector of forces, which can be
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accessed by various "output commands"_Section_howto.html#4_15. The
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scalar is the potential energy discussed above. The vector is the
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total force on the group of atoms before the forces on individual
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atoms are changed by the fix. The scalar vector values calculated by
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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 "run"_run.html command.
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The forces due to this fix are imposed during an energy minimization,
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invoked by the "minimize"_minimize.html command.
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IMPORTANT NOTE: If you want the fictitious potential energy associated
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with the added forces to be included in the total potential energy of
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the system (the quantity being minimized), you MUST enable the
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"fix_modify"_fix_modify.html {energy} option for this fix.
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[Restrictions:] none
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[Related commands:]
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"fix setforce"_fix_setforce.html, "fix aveforce"_fix_aveforce.html
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[Default:] none
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