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< li > fix lb/momentum command< / li >
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< span id = "index-0" > < / span > < h1 > fix lb/momentum command< a class = "headerlink" href = "#fix-lb-momentum-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
< div class = "section" id = "syntax" >
< h2 > Syntax< a class = "headerlink" href = "#syntax" title = "Permalink to this headline" > ¶< / a > < / h2 >
< div class = "highlight-python" > < div class = "highlight" > < pre > fix ID group-ID lb/momentum nevery keyword values ...
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< li > ID, group-ID are documented in the < a class = "reference internal" href = "fix.html" > < em > fix< / em > < / a > command< / li >
< li > lb/momentum = style name of this fix command< / li >
< li > nevery = adjust the momentum every this many timesteps< / li >
< li > zero or more keyword/value pairs may be appended< / li >
< li > keyword = < em > linear< / em > < / li >
< / ul >
< pre class = "literal-block" >
< em > linear< / em > values = xflag yflag zflag
xflag,yflag,zflag = 0/1 to exclude/include each dimension.
< / pre >
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< 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 1 sphere lb/momentum
fix 1 all lb/momentum linear 1 1 0
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< div class = "section" id = "description" >
< h2 > Description< a class = "headerlink" href = "#description" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > This fix is based on the < a class = "reference internal" href = "fix_momentum.html" > < em > fix momentum< / em > < / a > command, and
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was created to be used in place of that command, when a
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lattice-Boltzmann fluid is present.< / p >
< p > Zero the total linear momentum of the system, including both the atoms
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specified by group-ID and the lattice-Boltzmann fluid every nevery
timesteps. This is accomplished by adjusting the particle velocities
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and the fluid velocities at each lattice site.< / p >
< div class = "admonition note" >
< p class = "first admonition-title" > Note< / p >
< p class = "last" > This fix only considers the linear momentum of the system.< / p >
< / div >
< p > By default, the subtraction is performed for each dimension. This can
be changed by specifying the keyword < em > linear< / em > , along with a set of
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three flags set to 0/1 in order to exclude/ include the corresponding
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dimension.< / p >
< / div >
< 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
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are relevant to this fix. No global or per-atom quantities are stored
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by this fix for access by various < span class = "xref std std-ref" > output commands< / span > . 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.
This fix is not invoked during < a class = "reference internal" href = "minimize.html" > < em > energy minimization< / em > < / a > .< / p >
< / div >
< div class = "section" id = "restrictions" >
< h2 > Restrictions< a class = "headerlink" href = "#restrictions" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > Can only be used if a lattice-Boltzmann fluid has been created via the
< a class = "reference internal" href = "fix_lb_fluid.html" > < em > fix lb/fluid< / em > < / a > command, and must come after this
command.< / p >
< p > This fix is part of the USER-LB package. It is 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 >
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< 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_momentum.html" > < em > fix momentum< / em > < / a > , < a class = "reference internal" href = "fix_lb_fluid.html" > < em > fix lb/fluid< / em > < / a > < / p >
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< div class = "section" id = "default" >
< h2 > Default< a class = "headerlink" href = "#default" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > Zeros the total system linear momentum in each dimension.< / p >
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