forked from lijiext/lammps
82 lines
2.9 KiB
HTML
82 lines
2.9 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_modify 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_modify fix-ID keyword value ...
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</PRE>
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<UL><LI>fix-ID = ID of the fix to modify
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<LI>one or more keyword/value pairs may be appended
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<LI>keyword = <I>temp</I> or <I>press</I> or <I>energy</I>
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<PRE> <I>temp</I> value = compute ID that calculates a temperature
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<I>press</I> value = compute ID that calculates a pressure
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<I>energy</I> value = <I>yes</I> or <I>no</I>
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</PRE>
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>fix_modify 3 temp myTemp press myPress
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fix_modify 1 energy yes
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Modify one or more parameters of a previously defined fix. Only
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specific fix styles support specific parameters. See the doc pages
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for individual fix commands for info on which ones support which
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fix_modify parameters.
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</P>
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<P>The <I>temp</I> keyword is used to determine how a fix computes
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temperature. The specified compute ID must have been previously
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defined by the user via the <A HREF = "compute.html">compute</A> command and it must
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be a style of compute that calculates a temperature. All fixes that
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compute temperatures define their own compute by default, as described
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in their documentation. Thus this option allows the user to override
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the default method for computing T.
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</P>
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<P>The <I>press</I> keyword is used to determine how a fix computes pressure.
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The specified compute ID must have been previously defined by the user
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via the <A HREF = "compute.html">compute</A> command and it must be a style of
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compute that calculates a pressure. All fixes that compute pressures
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define their own compute by default, as described in their
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documentation. Thus this option allows the user to override the
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default method for computing P.
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</P>
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<P>For fixes that calculate a contribution to the potential energy of the
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system, the <I>energy</I> keyword will include that contribution in
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thermodynamic output of potential energy. See the
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<A HREF = "thermo_style.html">thermo_style</A> command for info on how potential
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energy is output. The contribution by itself can be printed by using
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the keyword f_ID in the thermo_style custom command, where ID is the
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fix-ID of the appropriate fix. Note that you must use this setting
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for a fix if you are using it when performing an <A HREF = "minimize.html">energy
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minimization</A> and if you want the energy and forces it
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produces to be part of the optimization criteria.
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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 = "fix.html">fix</A>, <A HREF = "compute_temp.html">compute temp</A>, <A HREF = "compute_pressure.html">compute
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pressure</A>, <A HREF = "thermo_style.html">thermo_style</A>
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</P>
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<P><B>Default:</B>
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</P>
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<P>The option defaults are temp = ID defined by fix, press = ID defined
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by fix, energy = no.
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</P>
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</HTML>
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