122 lines
4.5 KiB
Plaintext
122 lines
4.5 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 halt command :h3
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[Syntax:]
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fix ID group-ID halt N attribute operator avalue keyword value ... :pre
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ID, group-ID are documented in "fix"_fix.html command :ulb,l
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halt = style name of this fix command :l
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N = check halt condition every N steps :l
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attribute = hstyle or v_name :l
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hstyle = {bondmax}
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v_name = name of "equal-style variable"_variable.html :pre
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operator = "<" or "<=" or ">" or ">=" or "==" or "!=" or "|^" :l
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avalue = numeric value to compare attribute to :l
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string = text string to print with optional variable names :l
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zero or more keyword/value pairs may be appended :l
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keyword = {error} :l
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{error} value = {hard} or {soft} or {continue} :pre
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:ule
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[Examples:]
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fix 10 all halt 1 bondmax > 1.5
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fix 10 all print 10 v_myCheck != 0 error soft :pre
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[Description:]
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Check a condition every N steps during a simulation run. N must be >=
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1. If the condition is met, exit the run immediately. In this
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context a "run" can be dynamics or minimization iterations, as
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specified by the "run"_run.html or "minimize"_minimize.html command.
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The specified group-ID is ignored by this fix.
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The specified {attribute} can be one of the {hstyle} options listed
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above, or an "equal-style variable"_variable.html referenced as
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{v_name}, where "name" is the name of a variable that has been defined
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previously in the input script.
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The only {hstyle} option currently implemented is {bondmax}. This
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will loop over all bonds in the system, compute their current
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lengths, and set {attribute} to the longest bond distance.
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Equal-style variables evaluate to a numeric value. See the
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"variable"_variable.html command for a description. They calculate
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formulas which can involve mathematical operations, atom properties,
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group properties, thermodynamic properties, global values calculated
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by a "compute"_compute.html or "fix"_fix.html, or references to other
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"variables"_variable.html. Thus they are a very general means of
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computing some attribute of the current system. For example, the
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following "bondmax" variable will calculate the same quantity as the
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hstyle = bondmax option.
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compute bdist all bond/local dist
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compute bmax all reduce max c_bdist
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variable bondmax equal c_bmax :pre
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Thus these two versions of a fix halt command will do the same thing:
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fix 10 all halt 1 bondmax > 1.5
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fix 10 all halt 1 v_bondmax > 1.5 :pre
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The version with "bondmax" will just run somewhat faster, due to less
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overhead in computing bond lengths and not storing them in a separate
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compute.
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The choice of operators listed above are the usual comparison
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operators. The XOR operation (exclusive or) is also included as "|^".
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In this context, XOR means that if either the attribute or avalue is
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0.0 and the other is non-zero, then the result is "true". Otherwise
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it is "false".
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The specified {avalue} must be a numeric value.
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:line
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The optional {error} keyword determines how the current run is halted.
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If its value is {hard}, then LAMMPS will stop with an error message.
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If its value is {soft}, LAMMPS will exit the current run, but continue
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to execute subsequent commands in the input script. However,
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additional "run"_run.html or "minimize"_minimize.html commands will be
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skipped. For example, this allows a script to output the current
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state of the system, e.g. via a "write_dump"_write_dump.html or
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"write_restart"_write_restart.html command.
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If its value is {continue}, the behavior is the same as for {soft},
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except subsequent subsequent "run"_run.html or
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"minimize"_minimize.html commands are executed. This allows your
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script to remedy the condition that triggered the halt, if necessary.
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Note that you may wish use the "unfix"_unfix.html command on the fix
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halt ID, so that the same condition is not immediately triggered in a
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subsequent run.
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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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"variable"_variable.html
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[Default:]
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The option defaults are error = hard.
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