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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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<H3>fix ave/atom command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID ave/atom Nevery Nrepeat Nfreq compute-ID
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
<LI>ave/atom = style name of this fix command
<LI>Nevery = calculate property every this many timesteps
<LI>Nrepeat = # of times to repeat the Nevery calculation before averaging
<LI>Nfreq = timestep frequency at which the average value is calculated
<LI>compute-ID = ID of per-atom compute that performs the calculation
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix 1 all ave/atom 1 100 100 myVx
fix 1 all ave/atom 10 20 1000 my_epair
</PRE>
<P><B>Description:</B>
</P>
<P>Calculate one or more time-averaged per-atom quantities every few
timesteps. The results of this calculation can be spatially averaged
via the <A HREF = "fix_ave_spatial.html">fix ave/spatial</A> command or output
to a file via the <A HREF = "dump.html">dump custom</A> command.
</P>
<P>The <I>compute-ID</I> specifies a <A HREF = "compute.html">compute</A> which calculates
the desired property. It must be a per-atom compute (one with the
word "atom" in its style name) that calculates one or more values for
each atom, as opposed to a global compute. The compute must be
previously defined in the input script. Users can also write code for
their own compute styles and <A HREF = "Section_modify.html">add them to LAMMPS</A>.
</P>
<P>The <I>Nevery</I>, <I>Nrepeat</I>, and <I>Nfreq</I> arguments specify how the
property will be time-averaged. The final averaged value(s) are
computed every <I>Nfreq</I> timesteps. The average is over <I>Nrepeat</I>
values, computed in the preceeding portion of the simulation every
<I>Nevery</I> timesteps. Thus if Nevery=2, Nrepeat=6, and Nfreq=100, then
values on timesteps 90,92,94,96,98,100 will be used to compute the
final average at timestep 100. Similary for timesteps
190,192,194,196,198,200 at timestep 200, etc.
</P>
<P>If this fix is referenced by a <A HREF = "dump.html">dump custom</A> or <A HREF = "fix_ave_spatial.html">fix
ave/spatial</A> command, the time-averaged values
can only be accessed every <I>Nfreq</I> timesteps.
</P>
<P>If the compute calculates a single or multiple values per atom, then
fix ave/atom will also calculate one or multiple time-averaged
quantities per atom. This makes a difference in how the quantities
are referenced in a <A HREF = "dump.html">dump custom</A> command, e.g. c_ID versus
c_ID[2].
</P>
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
</P>
<P>No information about this fix is written to <A HREF = "restart.html">binary restart
files</A>. None of the <A HREF = "fix_modify.html">fix_modify</A> options
are relevant to this fix. No global scalar or vector quantities are
stored by this fix for access by various <A HREF = "Section_howto.html#4_15">output
commands</A>.
</P>
<P>This fix computes a scalar per-atom quantity or a vector of per-atom
quantities which can be accessed by the <A HREF = "dump.html">dump custom</A> or
<A HREF = "fix_ave_spatial.html">fix ave/spatial</A> commands, as discussed in <A HREF = "Section_howto.html#4_15">this
section</A>.
</P>
<P>No parameter of this fix can be used with the <I>start/stop</I> keywords of
the <A HREF = "run.html">run</A> command. This fix is not invoked during <A HREF = "minimize.html">energy
minimization</A>.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "compute.html">compute</A>, <A HREF = "fix_ave_spatial.html">fix ave/spatial</A>, <A HREF = "dump.html">dump
custom</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>
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