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Sat, Nov 23, 14:30
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text/html
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rLAMMPS lammps
fix_modify.html
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<HTML>
<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>
</CENTER>
<HR>
<H3>
fix_modify command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
fix_modify fix-ID keyword value ...
</PRE>
<UL><LI>
fix-ID = ID of the fix to modify
<LI>
one or more keyword/value pairs may be appended
<LI>
keyword =
<I>
temp
</I>
or
<I>
press
</I>
or
<I>
energy
</I>
<PRE>
<I>
temp
</I>
value = compute ID that calculates a temperature
<I>
press
</I>
value = compute ID that calculates a pressure
<I>
energy
</I>
value =
<I>
yes
</I>
or
<I>
no
</I>
</PRE>
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
fix_modify 3 temp myTemp press myPress
fix_modify 1 energy yes
</PRE>
<P><B>
Description:
</B>
</P>
<P>
Modify one or more parameters of a previously defined fix. Only
specific fix styles support specific parameters. See the doc pages
for individual fix commands for info on which ones support which
fix_modify parameters.
</P>
<P>
The
<I>
temp
</I>
keyword is used to determine how a fix computes
temperature. The specified compute ID must have been previously
defined by the user via the
<A
HREF =
"compute.html"
>
compute
</A>
command and it must
be a style of compute that calculates a temperature. All fixes that
compute temperatures define their own compute by default, as described
in their documentation. Thus this option allows the user to override
the default method for computing T.
</P>
<P>
The
<I>
press
</I>
keyword is used to determine how a fix computes pressure.
The specified compute ID must have been previously defined by the user
via the
<A
HREF =
"compute.html"
>
compute
</A>
command and it must be a style of
compute that calculates a pressure. All fixes that compute pressures
define their own compute by default, as described in their
documentation. Thus this option allows the user to override the
default method for computing P.
</P>
<P>
For fixes that calculate a contribution to the potential energy of the
system, the
<I>
energy
</I>
keyword will include that contribution in
thermodynamic output of potential energy. See the
<A
HREF =
"thermo_style.html"
>
thermo_style
</A>
command for info on how potential
energy is output. The contribution by itself can be printed by using
the keyword f_ID in the thermo_style custom command, where ID is the
fix-ID of the appropriate fix. Note that you must use this setting
for a fix if you are using it when performing an
<A
HREF =
"minimize.html"
>
energy
minimization
</A>
and if you want the energy and forces it
produces to be part of the optimization criteria.
</P>
<P><B>
Restrictions:
</B>
none
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"fix.html"
>
fix
</A>
,
<A
HREF =
"compute_temp.html"
>
compute temp
</A>
,
<A
HREF =
"compute_pressure.html"
>
compute
pressure
</A>
,
<A
HREF =
"thermo_style.html"
>
thermo_style
</A>
</P>
<P><B>
Default:
</B>
</P>
<P>
The option defaults are temp = ID defined by fix, press = ID defined
by fix, energy = no.
</P>
</HTML>
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