forked from lijiext/lammps
63 lines
2.2 KiB
HTML
63 lines
2.2 KiB
HTML
<HTML>
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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</CENTER>
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<HR>
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<H3>fix print command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>fix ID group-ID print N string
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
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<LI>print = style name of this fix command
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<LI>N = print every N steps
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<LI>string = text string to print with optional variable names
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>fix extra all print 100 "Coords of marker atom = $x $y $z"
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Print a text string to the screen and logfile every N steps during a
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simulation run. This can be used for diagnostic purposes or even as a
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debugging tool to monitor some quantity during a run. The text string
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must be a single argument, so it should be enclosed in double quotes
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if it is more than one word. If it contains variables ($a thru $z) it
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must be enclosed in double quotes to insure they are not evaluated
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when the input script is read, but will instead be evaluated when the
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string is printed.
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</P>
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<P>See the <A HREF = "variable.html">variable</A> command for a description of <I>equal</I>
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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.
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</P>
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<P>Note that if <I>equal</I>-style variables are used in the print line which
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contain <A HREF = "thermo_style.html">thermo_style custom</A> keywords for potential
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energy such as pe, eng, evdwl, ebond, etc, they will only be
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up-to-date on timesteps where thermodynamics are computed. Hence, if
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you output thermodynamics every 100 steps, but issue a fix print
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command with N = 2 that contains such a variable, the printed value
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will only be current on timesteps that are a multiple of 100. This is
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because the potential functions in LAMMPS (pairwise, bond, etc) only
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compute energies on timesteps when thermodynamic output is being
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performed.
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</P>
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<P><B>Restrictions:</B> none
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "variable.html">variable</A>, <A HREF = "print.html">print</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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