forked from lijiext/lammps
73 lines
2.5 KiB
Plaintext
73 lines
2.5 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 wall/reflect command :h3
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[Syntax:]
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fix ID group-ID wall/reflect keyword ... :pre
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ID, group-ID are documented in "fix"_fix.html command
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wall/reflect = style name of this fix command
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one or more keyword/value pairs may be appended
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keyword = {xlo} or {xhi} or {ylo} or {yhi} or {zlo} or {zhi} :ul
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[Examples:]
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fix xwalls all wall/reflect xlo xhi
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fix walls all wall/reflect xlo ylo zlo xhi yhi zhi :pre
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[Description:]
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Bound the simulation with one or more walls which reflect particles
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when they attempt to move thru them.
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Reflection means that if an atom moves outside the box on a timestep
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by a distance delta (e.g. due to "fix nve"_fix_nve.html), then it is
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put back inside the box by the same delta and the sign of the
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corresponding component of its velocity is flipped.
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When used in conjunction with "fix nve"_fix_nve.html and "run_style
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verlet"_run_style.html, the resultant time-integration algorithm is
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equivalent to the primitive splitting algorithm (PSA) described by
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"Bond"_#Bond. Because each reflection event divides
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the corresponding timestep asymmetrically, energy conservation is only
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satisfied to O(dt), rather than to O(dt^2) as it would be for
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velocity-Verlet integration without reflective walls.
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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 scalar or vector or per-atom
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quantities are stored by this fix for access by various "output
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commands"_Section_howto.html#4_15. No parameter of this fix can be
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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:]
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Any dimension (xyz) that has a reflecting wall must be non-periodic.
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A reflecting wall should not be used with rigid bodies such as those
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defined by a "fix rigid" command. This is because the wall/reflect
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displaces atoms directly rather than exerts a force on them. For
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rigid bodies, use a soft wall instead, such as "fix
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wall/lj93"_fix_wall_lj93.html. LAMMPS will flag the use of a rigid
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fix with fix wall/reflect with a warning, but will not generate an
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error.
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[Related commands:]
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"fix wall/lj93"_fix_wall_lj93.html command
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[Default:] none
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:link(Bond)
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[(Bond)] Bond and Leimkuhler, SIAM J Sci Comput, 30, p 134 (2007).
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