forked from lijiext/lammps
70 lines
2.3 KiB
Plaintext
70 lines
2.3 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 momentum command :h3
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[Syntax:]
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fix ID group-ID momentum N keyword values ... :pre
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ID, group-ID are documented in "fix"_fix.html command :ulb,l
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momentum = style name of this fix command :l
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N = adjust the momentum every this many timesteps
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one or more keyword/value pairs may be appended :l
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keyword = {linear} or {angular} :l
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{linear} values = xflag yflag zflag
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xflag,yflag,zflag = 0/1 to exclude/include each dimension
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{angular} values = none :pre
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:ule
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[Examples:]
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fix 1 all momentum 1 linear 1 1 0
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fix 1 all momentum 100 linear 1 1 1 angular :pre
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[Description:]
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Zero the linear and/or angular momentum of the group of atoms every N
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timesteps by adjusting the velocities of the atoms. One (or both) of
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the {linear} or {angular} keywords must be specified.
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If the {linear} keyword is used, the linear momentum is zeroed by
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subtracting the center-of-mass velocity of the group from each atom.
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This does not change the relative velocity of any pair of atoms. One
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or more dimensions can be excluded from this operation by setting the
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corresponding flag to 0.
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If the {angular} keyword is used, the angular momentum is zeroed by
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subtracting a rotational component from each atom.
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This command can be used to insure the entire collection of atoms (or
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a subset of them) does not drift or rotate during the simulation due
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to random perturbations (e.g. "fix langevin"_fix_langevin.html
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thermostatting).
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Note that the "velocity"_velocity.html command can be used to create
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initial velocities with zero aggregate linear and/or angular momentum.
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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. None of the "fix_modify"_fix_modify.html options
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are relevant to this fix. No global or per-atom quantities are stored
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by this fix for access by various "output
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commands"_Section_howto.html#howto_15. No parameter of this fix can
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be used with the {start/stop} keywords of the "run"_run.html command.
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This fix is not invoked during "energy minimization"_minimize.html.
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[Restrictions:] none
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[Related commands:]
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"fix recenter"_fix_recenter.html, "velocity"_velocity.html
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[Default:] none
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