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<div class="section" id="fix-setforce-command">
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<span id="index-0"></span><h1>fix setforce command<a class="headerlink" href="#fix-setforce-command" title="Permalink to this headline">¶</a></h1>
|
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</div>
|
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<div class="section" id="fix-setforce-cuda-command">
|
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<h1>fix setforce/cuda command<a class="headerlink" href="#fix-setforce-cuda-command" title="Permalink to this headline">¶</a></h1>
|
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<div class="section" id="syntax">
|
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<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
|
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<div class="highlight-python"><div class="highlight"><pre>fix ID group-ID setforce fx fy fz keyword value ...
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</pre></div>
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</div>
|
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<ul class="simple">
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<li>ID, group-ID are documented in <a class="reference internal" href="fix.html"><em>fix</em></a> command</li>
|
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<li>setforce = style name of this fix command</li>
|
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<li>fx,fy,fz = force component values</li>
|
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<li>any of fx,fy,fz can be a variable (see below)</li>
|
||||
<li>zero or more keyword/value pairs may be appended to args</li>
|
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<li>keyword = <em>region</em></li>
|
||||
</ul>
|
||||
<pre class="literal-block">
|
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<em>region</em> value = region-ID
|
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region-ID = ID of region atoms must be in to have added force
|
||||
</pre>
|
||||
</div>
|
||||
<div class="section" id="examples">
|
||||
<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
|
||||
<div class="highlight-python"><div class="highlight"><pre>fix freeze indenter setforce 0.0 0.0 0.0
|
||||
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<HR>
|
||||
|
||||
<H3>fix setforce command
|
||||
</H3>
|
||||
<H3>fix setforce/cuda command
|
||||
</H3>
|
||||
<P><B>Syntax:</B>
|
||||
</P>
|
||||
<PRE>fix ID group-ID setforce fx fy fz keyword value ...
|
||||
</PRE>
|
||||
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
|
||||
|
||||
<LI>setforce = style name of this fix command
|
||||
|
||||
<LI>fx,fy,fz = force component values
|
||||
|
||||
<LI>any of fx,fy,fz can be a variable (see below)
|
||||
|
||||
<LI>zero or more keyword/value pairs may be appended to args
|
||||
|
||||
<LI>keyword = <I>region</I>
|
||||
|
||||
<PRE> <I>region</I> value = region-ID
|
||||
region-ID = ID of region atoms must be in to have added force
|
||||
</PRE>
|
||||
|
||||
</UL>
|
||||
<P><B>Examples:</B>
|
||||
</P>
|
||||
<PRE>fix freeze indenter setforce 0.0 0.0 0.0
|
||||
fix 2 edge setforce NULL 0.0 0.0
|
||||
fix 2 edge setforce NULL 0.0 v_oscillate
|
||||
</pre></div>
|
||||
</div>
|
||||
</div>
|
||||
<div class="section" id="description">
|
||||
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
|
||||
<p>Set each component of force on each atom in the group to the specified
|
||||
fix 2 edge setforce NULL 0.0 v_oscillate
|
||||
</PRE>
|
||||
<P><B>Description:</B>
|
||||
</P>
|
||||
<P>Set each component of force on each atom in the group to the specified
|
||||
values fx,fy,fz. This erases all previously computed forces on the
|
||||
atom, though additional fixes could add new forces. This command can
|
||||
be used to freeze certain atoms in the simulation by zeroing their
|
||||
force, either for running dynamics or performing an energy
|
||||
minimization. For dynamics, this assumes their initial velocity is
|
||||
also zero.</p>
|
||||
<p>Any of the fx,fy,fz values can be specified as NULL which means do not
|
||||
alter the force component in that dimension.</p>
|
||||
<p>Any of the 3 quantities defining the force components can be specified
|
||||
as an equal-style or atom-style <a class="reference internal" href="variable.html"><em>variable</em></a>, namely <em>fx</em>,
|
||||
<em>fy</em>, <em>fz</em>. If the value is a variable, it should be specified as
|
||||
also zero.
|
||||
</P>
|
||||
<P>Any of the fx,fy,fz values can be specified as NULL which means do not
|
||||
alter the force component in that dimension.
|
||||
</P>
|
||||
<P>Any of the 3 quantities defining the force components can be specified
|
||||
as an equal-style or atom-style <A HREF = "variable.html">variable</A>, namely <I>fx</I>,
|
||||
<I>fy</I>, <I>fz</I>. If the value is a variable, it should be specified as
|
||||
v_name, where name is the variable name. In this case, the variable
|
||||
will be evaluated each timestep, and its value used to determine the
|
||||
force component.</p>
|
||||
<p>Equal-style variables can specify formulas with various mathematical
|
||||
functions, and include <a class="reference internal" href="thermo_style.html"><em>thermo_style</em></a> command
|
||||
force component.
|
||||
</P>
|
||||
<P>Equal-style variables can specify formulas with various mathematical
|
||||
functions, and include <A HREF = "thermo_style.html">thermo_style</A> command
|
||||
keywords for the simulation box parameters and timestep and elapsed
|
||||
time. Thus it is easy to specify a time-dependent force field.</p>
|
||||
<p>Atom-style variables can specify the same formulas as equal-style
|
||||
time. Thus it is easy to specify a time-dependent force field.
|
||||
</P>
|
||||
<P>Atom-style variables can specify the same formulas as equal-style
|
||||
variables but can also include per-atom values, such as atom
|
||||
coordinates. Thus it is easy to specify a spatially-dependent force
|
||||
field with optional time-dependence as well.</p>
|
||||
<p>If the <em>region</em> keyword is used, the atom must also be in the
|
||||
specified geometric <a class="reference internal" href="region.html"><em>region</em></a> in order to have force added
|
||||
to it.</p>
|
||||
<hr class="docutils" />
|
||||
<p>Styles with a <em>cuda</em> suffix are functionally the same as the
|
||||
field with optional time-dependence as well.
|
||||
</P>
|
||||
<P>If the <I>region</I> keyword is used, the atom must also be in the
|
||||
specified geometric <A HREF = "region.html">region</A> in order to have force added
|
||||
to it.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<P>Styles with a <I>cuda</I> suffix are functionally the same as the
|
||||
corresponding style without the suffix. They have been optimized to
|
||||
run faster, depending on your available hardware, as discussed in
|
||||
<a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></a> of the manual. The
|
||||
<A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual. The
|
||||
accelerated styles take the same arguments and should produce the same
|
||||
results, except for round-off and precision issues.</p>
|
||||
<p>These accelerated styles are part of the USER-CUDA package. They are
|
||||
only enabled if LAMMPS was built with that package. See the <a class="reference internal" href="Section_start.html#start-3"><span>Making LAMMPS</span></a> section for more info.</p>
|
||||
<p>You can specify the accelerated styles explicitly in your input script
|
||||
by including their suffix, or you can use the <a class="reference internal" href="Section_start.html#start-7"><span>-suffix command-line switch</span></a> when you invoke LAMMPS, or you can
|
||||
use the <a class="reference internal" href="suffix.html"><em>suffix</em></a> command in your input script.</p>
|
||||
<p>See <a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></a> of the manual for
|
||||
more instructions on how to use the accelerated styles effectively.</p>
|
||||
</div>
|
||||
<hr class="docutils" />
|
||||
<div class="section" id="restart-fix-modify-output-run-start-stop-minimize-info">
|
||||
<h2>Restart, fix_modify, output, run start/stop, minimize info<a class="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 <a class="reference internal" href="restart.html"><em>binary restart files</em></a>. None of the <a class="reference internal" href="fix_modify.html"><em>fix_modify</em></a> options
|
||||
are relevant to this fix.</p>
|
||||
<p>This fix computes a global 3-vector of forces, which can be accessed
|
||||
by various <a class="reference internal" href="Section_howto.html#howto-15"><span>output commands</span></a>. This is the
|
||||
results, except for round-off and precision issues.
|
||||
</P>
|
||||
<P>These accelerated styles are part of the USER-CUDA package. They are
|
||||
only enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#start_3">Making
|
||||
LAMMPS</A> section for more info.
|
||||
</P>
|
||||
<P>You can specify the accelerated styles explicitly in your input script
|
||||
by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
|
||||
switch</A> when you invoke LAMMPS, or you can
|
||||
use the <A HREF = "suffix.html">suffix</A> command in your input script.
|
||||
</P>
|
||||
<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
|
||||
more instructions on how to use the accelerated styles effectively.
|
||||
</P>
|
||||
<HR>
|
||||
|
||||
<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.
|
||||
</P>
|
||||
<P>This fix computes a global 3-vector of forces, which can be accessed
|
||||
by various <A HREF = "Section_howto.html#howto_15">output commands</A>. This is the
|
||||
total force on the group of atoms before the forces on individual
|
||||
atoms are changed by the fix. The vector values calculated by this
|
||||
fix are “extensive”.</p>
|
||||
<p>No parameter of this fix can be used with the <em>start/stop</em> keywords of
|
||||
the <a class="reference internal" href="run.html"><em>run</em></a> command.</p>
|
||||
<p>The forces due to this fix are imposed during an energy minimization,
|
||||
invoked by the <a class="reference internal" href="minimize.html"><em>minimize</em></a> command, but you cannot set
|
||||
fix are "extensive".
|
||||
</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.
|
||||
</P>
|
||||
<P>The forces due to this fix are imposed during an energy minimization,
|
||||
invoked by the <A HREF = "minimize.html">minimize</A> command, but you cannot set
|
||||
forces to any value besides zero when performing a minimization. Use
|
||||
the <a class="reference internal" href="fix_addforce.html"><em>fix addforce</em></a> command if you want to apply a
|
||||
non-zero force to atoms during a minimization.</p>
|
||||
</div>
|
||||
<div class="section" id="restrictions">
|
||||
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></h2>
|
||||
<blockquote>
|
||||
<div>none</div></blockquote>
|
||||
</div>
|
||||
<div class="section" id="related-commands">
|
||||
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
|
||||
<p><a class="reference internal" href="fix_addforce.html"><em>fix addforce</em></a>, <a class="reference internal" href="fix_aveforce.html"><em>fix aveforce</em></a></p>
|
||||
<p><strong>Default:</strong> none</p>
|
||||
</div>
|
||||
</div>
|
||||
|
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|
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</div>
|
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</div>
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<footer>
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<hr/>
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|
||||
the <A HREF = "fix_addforce.html">fix addforce</A> command if you want to apply a
|
||||
non-zero force to atoms during a minimization.
|
||||
</P>
|
||||
<P><B>Restrictions:</B> none
|
||||
</P>
|
||||
<P><B>Related commands:</B>
|
||||
</P>
|
||||
<P><A HREF = "fix_addforce.html">fix addforce</A>, <A HREF = "fix_aveforce.html">fix aveforce</A>
|
||||
</P>
|
||||
<P><B>Default:</B> none
|
||||
</P>
|
||||
</HTML>
|
||||
|
||||
Reference in New Issue
Block a user