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< title > pair_style lj/mdf command — LAMMPS documentation< / title >
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< li > pair_style lj/mdf command< / li >
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< div class = "section" id = "pair-style-lj-mdf-command" >
< span id = "index-0" > < / span > < h1 > pair_style lj/mdf command< a class = "headerlink" href = "#pair-style-lj-mdf-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
< / div >
< div class = "section" id = "pair-style-buck-mdf-command" >
< h1 > pair_style buck/mdf command< a class = "headerlink" href = "#pair-style-buck-mdf-command" title = "Permalink to this headline" > ¶< / a > < / h1 >
< / div >
< div class = "section" id = "pair-style-lennard-mdf-command" >
< h1 > pair_style lennard/mdf command< a class = "headerlink" href = "#pair-style-lennard-mdf-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 > pair_style style args
< / pre > < / div >
< / div >
< ul class = "simple" >
< li > style = < em > lj/mdf< / em > or < em > buck/mdf< / em > or < em > lennard/mdf< / em > < / li >
< li > args = list of arguments for a particular style< / li >
< / ul >
< pre class = "literal-block" >
< em > lj/mdf< / em > args = cutoff1 cutoff2
cutoff1 = inner cutoff for the start of the tapering function
cutoff1 = out cutoff for the end of the tapering function
< em > buck/mdf< / em > args = cutoff1 cutoff2
cutoff1 = inner cutoff for the start of the tapering function
cutoff1 = out cutoff for the end of the tapering function
< em > lennard/mdf< / em > args = cutoff1 cutoff2
cutoff1 = inner cutoff for the start of the tapering function
cutoff1 = out cutoff for the end of the tapering function
< / 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 > pair_style lj/mdf 2.5 3.0
pair_coeff * * 1 1
pair_coeff 1 1 1 1.1 2.8 3.0 3.2
< / pre > < / div >
< / div >
< div class = "highlight-python" > < div class = "highlight" > < pre > pair_style buck 2.5 3.0
pair_coeff * * 100.0 1.5 200.0
pair_coeff * * 100.0 1.5 200.0 3.0 3.5
< / pre > < / div >
< / div >
< div class = "highlight-python" > < div class = "highlight" > < pre > pair_style lennard/mdf 2.5 3.0
pair_coeff * * 1 1
pair_coeff 1 1 1 1.1 2.8 3.0 3.2
< / pre > < / div >
< / div >
< / div >
< div class = "section" id = "description" >
< h2 > Description< a class = "headerlink" href = "#description" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > The < em > lj/mdf< / em > , < em > buck/mdf< / em > and < em > lennard/mdf< / em > compute the standard 12-6
Lennard-Jones and Buckingham potential with the addition of a taper
function that ramps the energy and force smoothly to zero between an
inner and outer cutoff.< / p >
< img alt = "Eqs/pair_mdf-1.jpg" class = "align-center" src = "Eqs/pair_mdf-1.jpg" / >
< p > The tapering, < em > f(r)< / em > , is done by using the Mei, Davenport, Fernando
function < a class = "reference internal" href = "#mei" > < span > (Mei)< / span > < / a > .< / p >
< img alt = "Eqs/pair_mdf-2.jpg" class = "align-center" src = "Eqs/pair_mdf-2.jpg" / >
< p > where< / p >
< img alt = "Eqs/pair_mdf-3.jpg" class = "align-center" src = "Eqs/pair_mdf-3.jpg" / >
< p > Here < em > r_m< / em > is the inner cutoff radius and < em > r_cut< / em > is the outer cutoff
radius.< / p >
< hr class = "docutils" / >
< p > For the < em > lj/mdf< / em > pair_style, the potential energy, < em > E(r)< / em > , is the
standard 12-6 Lennard-Jones written in the epsilon/sigma form:< / p >
< img alt = "Eqs/pair_mdf-4.jpg" class = "align-center" src = "Eqs/pair_mdf-4.jpg" / >
< p > The following coefficients must be defined for each pair of atoms
types via the pair_coeff command as in the examples above, or in the
data file or restart files read by the < a class = "reference internal" href = "read_data.html" > < em > read_data< / em > < / a > or
< a class = "reference internal" href = "read_restart.html" > < em > read_restart commands< / em > < / a > , or by mixing as described
below:< / p >
< ul class = "simple" >
< li > epsilon (energy units)< / li >
< li > sigma (distance units)< / li >
< li > r_m (distance units)< / li >
< li > r_*cut* (distance units)< / li >
< / ul >
< hr class = "docutils" / >
< p > For the < em > buck/mdf< / em > pair_style, the potential energy, < em > E(r)< / em > , is the
standard 12-6 Lennard-Jones written in the epsilon/sigma form:< / p >
< img alt = "Eqs/pair_mdf-5.jpg" class = "align-center" src = "Eqs/pair_mdf-5.jpg" / >
< ul class = "simple" >
< li > A (energy units)< / li >
< li > rho (distance units)< / li >
< li > C (energy-distance^6 units)< / li >
< li > r_m (distance units)< / li >
< li > r_*cut*$ (distance units)< / li >
< / ul >
< hr class = "docutils" / >
< p > For the < em > lennard/mdf< / em > pair_style, the potential energy, < em > E(r)< / em > , is the
standard 12-6 Lennard-Jones written in the $A/B$ form:< / p >
< img alt = "Eqs/pair_mdf-6.jpg" class = "align-center" src = "Eqs/pair_mdf-6.jpg" / >
< p > The following coefficients must be defined for each pair of atoms
types via the pair_coeff command as in the examples above, or in the
data file or restart files read by the read_data or read_restart
commands, or by mixing as described below:< / p >
< ul class = "simple" >
< li > A (energy-distance^12 units)< / li >
< li > B (energy-distance^6 units)< / li >
< li > r_m (distance units)< / li >
< li > r_*cut* (distance units)< / li >
< / ul >
< hr class = "docutils" / >
< p > < strong > Mixing, shift, table, tail correction, restart, rRESPA info< / strong > :< / p >
< p > For atom type pairs I,J and I != J, the epsilon and sigma coefficients
and cutoff distance for all of the lj/cut pair styles can be mixed.
The default mix value is < em > geometric< / em > . See the “ pair_modify” command
for details.< / p >
< p > All of the < em > lj/cut< / em > pair styles support the
< a class = "reference internal" href = "pair_modify.html" > < em > pair_modify< / em > < / a > shift option for the energy of the
Lennard-Jones portion of the pair interaction.< / p >
< p > The < em > lj/cut/coul/long< / em > and < em > lj/cut/tip4p/long< / em > pair styles support the
< a class = "reference internal" href = "pair_modify.html" > < em > pair_modify< / em > < / a > table option since they can tabulate
the short-range portion of the long-range Coulombic interaction.< / p >
< p > All of the < em > lj/cut< / em > pair styles support the
< a class = "reference internal" href = "pair_modify.html" > < em > pair_modify< / em > < / a > tail option for adding a long-range
tail correction to the energy and pressure for the Lennard-Jones
portion of the pair interaction.< / p >
< p > All of the < em > lj/cut< / em > pair styles write their information to < a class = "reference internal" href = "restart.html" > < em > binary restart files< / em > < / a > , so pair_style and pair_coeff commands do
not need to be specified in an input script that reads a restart file.< / p >
< p > The < em > lj/cut< / em > and < em > lj/cut/coul/long< / em > pair styles support the use of the
< em > inner< / em > , < em > middle< / em > , and < em > outer< / em > keywords of the < a class = "reference internal" href = "run_style.html" > < em > run_style respa< / em > < / a > command, meaning the pairwise forces can be
partitioned by distance at different levels of the rRESPA hierarchy.
The other styles only support the < em > pair< / em > keyword of run_style respa.
See the < a class = "reference internal" href = "run_style.html" > < em > run_style< / em > < / a > command for details.< / p >
< / div >
< hr class = "docutils" / >
< div class = "section" id = "restrictions" >
< h2 > Restrictions< a class = "headerlink" href = "#restrictions" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > These pair styles can only be used if LAMMPS was built with the
USER-MISC package. See the < a class = "reference internal" href = "Section_start.html#start-3" > < span > Making LAMMPS< / span > < / a >
section for more info on packages.< / p >
< / 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 = "pair_coeff.html" > < em > pair_coeff< / em > < / a > < / p >
< p > < strong > Default:< / strong > none< / p >
< hr class = "docutils" / >
< p id = "mei" > < strong > (Mei)< / strong > Mei, Davenport, Fernando, Phys Rev B, 43 4653 (1991)< / p >
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2015-12-11 01:23:56 +08:00
© Copyright 2013 Sandia Corporation.
2015-12-10 06:46:13 +08:00
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