forked from lijiext/lammps
106 lines
4.1 KiB
Plaintext
106 lines
4.1 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,Commands_all.html)
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:line
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fix print command :h3
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[Syntax:]
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fix ID group-ID print N string keyword value ... :pre
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ID, group-ID are documented in "fix"_fix.html command :ulb,l
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print = style name of this fix command :l
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N = print every N steps; N can be a variable (see below) :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 = {file} or {append} or {screen} or {title} :l
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{file} value = filename
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{append} value = filename
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{screen} value = {yes} or {no}
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{title} value = string
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string = text to print as 1st line of output file :pre
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:ule
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[Examples:]
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fix extra all print 100 "Coords of marker atom = $x $y $z"
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fix extra all print 100 "Coords of marker atom = $x $y $z" file coord.txt :pre
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[Description:]
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Print a text string every N steps during a simulation run. This can
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be used for diagnostic purposes or as a debugging tool to monitor some
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quantity during a run. The text string must be a single argument, so
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it should be enclosed in double quotes if it is more than one word.
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If it contains variables it must be enclosed in double quotes to
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insure they are not evaluated when the input script line is read, but
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will instead be evaluated each time the string is printed.
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Instead of a numeric value, N can be specified as an "equal-style
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variable"_variable.html, which should be specified as v_name, where
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name is the variable name. In this case, the variable is evaluated at
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the beginning of a run to determine the [next] timestep at which the
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string will be written out. On that timestep, the variable will be
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evaluated again to determine the next timestep, etc.
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Thus the variable should return timestep values. See the stagger()
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and logfreq() and stride() math functions for "equal-style
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variables"_variable.html, as examples of useful functions to use in
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this context. For example, the following commands will print output at
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timesteps 10,20,30,100,200,300,1000,2000,etc:
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variable s equal logfreq(10,3,10)
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fix extra all print v_s "Coords of marker atom = $x $y $z" :pre
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The specified group-ID is ignored by this fix.
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See the "variable"_variable.html command for a description of {equal}
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style variables which are the most useful ones to use with the fix
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print command, since they are evaluated afresh each timestep that the
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fix print line is output. Equal-style variables calculate formulas
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involving mathematical operations, atom properties, group properties,
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thermodynamic properties, global values calculated by a
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"compute"_compute.html or "fix"_fix.html, or references to other
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"variables"_variable.html.
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If the {file} or {append} keyword is used, a filename is specified to
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which the output generated by this fix will be written. If {file} is
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used, then the filename is overwritten if it already exists. If
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{append} is used, then the filename is appended to if it already
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exists, or created if it does not exist.
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If the {screen} keyword is used, output by this fix to the screen and
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logfile can be turned on or off as desired.
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The {title} keyword allow specification of the string that will be
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printed as the first line of the output file, assuming the {file}
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keyword was used. By default, the title line is as follows:
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# Fix print output for fix ID :pre
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where ID is replaced with the fix-ID.
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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 commands"_Howto_output.html.
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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. This fix is not invoked during "energy
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minimization"_minimize.html.
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[Restrictions:] none
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[Related commands:]
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"variable"_variable.html, "print"_print.html
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[Default:]
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The option defaults are no file output, screen = yes, and title string
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as described above.
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