<divclass="highlight-python"><divclass="highlight"><pre>x,y,z,vx,vy,vz,fx,fy,fz = atom attribute (position, velocity, force component)
c_ID = per-atom vector calculated by a compute with ID
c_ID[I] = Ith column of per-atom array calculated by a compute with ID
f_ID = per-atom vector calculated by a fix with ID
f_ID[I] = Ith column of per-atom array calculated by a fix with ID
v_name = per-atom vector calculated by an atom-style variable with name
</pre></div>
</div>
</div>
<divclass="section"id="examples">
<h2>Examples<aclass="headerlink"href="#examples"title="Permalink to this headline">¶</a></h2>
<divclass="highlight-python"><divclass="highlight"><pre>fix 1 all ave/atom 1 100 100 vx vy vz
fix 1 all ave/atom 10 20 1000 c_my_stress[1]
</pre></div>
</div>
</div>
<divclass="section"id="description">
<h2>Description<aclass="headerlink"href="#description"title="Permalink to this headline">¶</a></h2>
<p>Use one or more per-atom vectors as inputs every few timesteps, and
average them atom by atom over longer timescales. The resulting
per-atom averages can be used by other <aclass="reference internal"href="Section_howto.html#howto-15"><span>output commands</span></a> such as the <aclass="reference internal"href="fix_ave_spatial.html"><em>fix ave/spatial</em></a> or <aclass="reference internal"href="dump.html"><em>dump custom</em></a> commands.</p>
<p>The group specified with the command means only atoms within the group
have their averages computed. Results are set to 0.0 for atoms not in
the group.</p>
<p>Each input value can be an atom attribute (position, velocity, force
component) or can be the result of a <aclass="reference internal"href="compute.html"><em>compute</em></a> or
<aclass="reference internal"href="fix.html"><em>fix</em></a> or the evaluation of an atom-style
<aclass="reference internal"href="variable.html"><em>variable</em></a>. In the latter cases, the compute, fix, or
variable must produce a per-atom vector, not a global quantity or
local quantity. If you wish to time-average global quantities from a
compute, fix, or variable, then see the <aclass="reference internal"href="fix_ave_time.html"><em>fix ave/time</em></a> command.</p>
<p><aclass="reference internal"href="compute.html"><em>Computes</em></a> that produce per-atom vectors or arrays are
those which have the word <em>atom</em> in their style name. See the doc
pages for individual <aclass="reference internal"href="fix.html"><em>fixes</em></a> to determine which ones produce
per-atom vectors or arrays. <aclass="reference internal"href="variable.html"><em>Variables</em></a> of style <em>atom</em>
are the only ones that can be used with this fix since they produce
per-atom vectors.</p>
<p>Each per-atom value of each input vector is averaged independently.</p>
<hrclass="docutils"/>
<p>The <em>Nevery</em>, <em>Nrepeat</em>, and <em>Nfreq</em> arguments specify on what
timesteps the input values will be used in order to contribute to the
average. The final averaged quantities are generated on timesteps
that are a multiple of <em>Nfreq</em>. The average is over <em>Nrepeat</em>
quantities, computed in the preceding portion of the simulation every
<em>Nevery</em> timesteps. <em>Nfreq</em> must be a multiple of <em>Nevery</em> and
<em>Nevery</em> must be non-zero even if <em>Nrepeat</em> is 1. Also, the timesteps
contributing to the average value cannot overlap, i.e. Nfreq >
(Nrepeat-1)*Nevery is required.</p>
<p>For example, 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
on timestep 100. Similarly for timesteps 190,192,194,196,198,200 on
timestep 200, etc.</p>
<hrclass="docutils"/>
<p>The atom attribute values (x,y,z,vx,vy,vz,fx,fy,fz) are
self-explanatory. Note that other atom attributes can be used as
inputs to this fix by using the <aclass="reference internal"href="compute_property_atom.html"><em>compute property/atom</em></a> command and then specifying
an input value from that compute.</p>
<divclass="admonition warning">
<pclass="first admonition-title">Warning</p>
<pclass="last">The x,y,z attributes are values that are re-wrapped
inside the periodic box whenever an atom crosses a periodic boundary.
Thus if you time average an atom that spends half its time on either
side of the periodic box, you will get a value in the middle of the
box. If this is not what you want, consider averaging unwrapped
coordinates, which can be provided by the <aclass="reference internal"href="compute_property_atom.html"><em>compute property/atom</em></a> command via its xu,yu,zu
attributes.</p>
</div>
<p>If a value begins with “<ahref="#id1"><spanclass="problematic"id="id2">c_</span></a>”, a compute ID must follow which has been
previously defined in the input script. If no bracketed term is
appended, the per-atom vector calculated by the compute is used. If a
bracketed term containing an index I is appended, the Ith column of
the per-atom array calculated by the compute is used. Users can also
write code for their own compute styles and <aclass="reference internal"href="Section_modify.html"><em>add them to LAMMPS</em></a>.</p>
<p>If a value begins with “<ahref="#id3"><spanclass="problematic"id="id4">f_</span></a>”, a fix ID must follow which has been
previously defined in the input script. If no bracketed term is
appended, the per-atom vector calculated by the fix is used. If a
bracketed term containing an index I is appended, the Ith column of
the per-atom array calculated by the fix is used. Note that some
fixes only produce their values on certain timesteps, which must be
compatible with <em>Nevery</em>, else an error will result. Users can also
write code for their own fix styles and <aclass="reference internal"href="Section_modify.html"><em>add them to LAMMPS</em></a>.</p>
<p>If a value begins with “<ahref="#id5"><spanclass="problematic"id="id6">v_</span></a>”, a variable name must follow which has
been previously defined in the input script as an <aclass="reference internal"href="variable.html"><em>atom-style variable</em></a> Variables of style <em>atom</em> can reference
thermodynamic keywords, or invoke other computes, fixes, or variables
when they are evaluated, so this is a very general means of generating
<h2>Restart, fix_modify, output, run start/stop, minimize info<aclass="headerlink"href="#restart-fix-modify-output-run-start-stop-minimize-info"title="Permalink to this headline">¶</a></h2>
<p>No information about this fix is written to <aclass="reference internal"href="restart.html"><em>binary restart files</em></a>. None of the <aclass="reference internal"href="fix_modify.html"><em>fix_modify</em></a> options
are relevant to this fix. No global scalar or vector quantities are
stored by this fix for access by various <aclass="reference internal"href="Section_howto.html#howto-15"><span>output commands</span></a>.</p>
<p>This fix produces a per-atom vector or array which can be accessed by
various <aclass="reference internal"href="Section_howto.html#howto-15"><span>output commands</span></a>. A vector is
produced if only a single quantity is averaged by this fix. If two or
more quantities are averaged, then an array of values is produced.
The per-atom values can only be accessed on timesteps that are
multiples of <em>Nfreq</em> since that is when averaging is performed.</p>
<p>No parameter of this fix can be used with the <em>start/stop</em> keywords of
the <aclass="reference internal"href="run.html"><em>run</em></a> command. This fix is not invoked during <aclass="reference internal"href="minimize.html"><em>energy minimization</em></a>.</p>
</div>
<divclass="section"id="restrictions">
<h2>Restrictions<aclass="headerlink"href="#restrictions"title="Permalink to this headline">¶</a></h2>
<blockquote>
<div>none</div></blockquote>
</div>
<divclass="section"id="related-commands">
<h2>Related commands<aclass="headerlink"href="#related-commands"title="Permalink to this headline">¶</a></h2>
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