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lammps/doc/src/pair_mdf.txt
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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)
:line
pair_style lj/mdf command :h3
pair_style buck/mdf command :h3
pair_style lennard/mdf command :h3
[Syntax:]
pair_style style args :pre
style = {lj/mdf} or {buck/mdf} or {lennard/mdf} :ulb,l
args = list of arguments for a particular style :l
{lj/mdf} args = cutoff1 cutoff2
cutoff1 = inner cutoff for the start of the tapering function
cutoff1 = out cutoff for the end of the tapering function
{buck/mdf} args = cutoff1 cutoff2
cutoff1 = inner cutoff for the start of the tapering function
cutoff1 = out cutoff for the end of the tapering function
{lennard/mdf} args = cutoff1 cutoff2
cutoff1 = inner cutoff for the start of the tapering function
cutoff1 = out cutoff for the end of the tapering function :pre
:ule
[Examples:]
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
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
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
[Description:]
The {lj/mdf}, {buck/mdf} and {lennard/mdf} 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.
:c,image(Eqs/pair_mdf-1.jpg)
The tapering, {f(r)}, is done by using the Mei, Davenport, Fernando
function "(Mei)"_#Mei.
:c,image(Eqs/pair_mdf-2.jpg)
where
:c,image(Eqs/pair_mdf-3.jpg)
Here {r_m} is the inner cutoff radius and {r_cut} is the outer cutoff
radius.
:line
For the {lj/mdf} pair_style, the potential energy, {E(r)}, is the
standard 12-6 Lennard-Jones written in the epsilon/sigma form:
:c,image(Eqs/pair_mdf-4.jpg)
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"_read_data.html or
"read_restart commands"_read_restart.html, or by mixing as described
below:
epsilon (energy units)
sigma (distance units)
r_m (distance units)
r_{cut} (distance units) :ul
:line
For the {buck/mdf} pair_style, the potential energy, {E(r)}, is the
standard Buckingham potential:
:c,image(Eqs/pair_mdf-5.jpg)
A (energy units)
\rho (distance units)
C (energy-distance^6 units)
r_m (distance units)
r_{cut}$ (distance units) :ul
:line
For the {lennard/mdf} pair_style, the potential energy, {E(r)}, is the
standard 12-6 Lennard-Jones written in the $A/B$ form:
:c,image(Eqs/pair_mdf-6.jpg)
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:
A (energy-distance^12 units)
B (energy-distance^6 units)
r_m (distance units)
r_{cut} (distance units) :ul
:line
[Mixing, shift, table, tail correction, restart, rRESPA info]:
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 {geometric}. See the "pair_modify" command
for details.
All of the {lj/cut} pair styles support the
"pair_modify"_pair_modify.html shift option for the energy of the
Lennard-Jones portion of the pair interaction.
The {lj/cut/coul/long} and {lj/cut/tip4p/long} pair styles support the
"pair_modify"_pair_modify.html table option since they can tabulate
the short-range portion of the long-range Coulombic interaction.
All of the {lj/cut} pair styles support the
"pair_modify"_pair_modify.html tail option for adding a long-range
tail correction to the energy and pressure for the Lennard-Jones
portion of the pair interaction.
All of the {lj/cut} pair styles write their information to "binary
restart files"_restart.html, so pair_style and pair_coeff commands do
not need to be specified in an input script that reads a restart file.
The {lj/cut} and {lj/cut/coul/long} pair styles support the use of the
{inner}, {middle}, and {outer} keywords of the "run_style
respa"_run_style.html command, meaning the pairwise forces can be
partitioned by distance at different levels of the rRESPA hierarchy.
The other styles only support the {pair} keyword of run_style respa.
See the "run_style"_run_style.html command for details.
:line
[Restrictions:]
These pair styles can only be used if LAMMPS was built with the
USER-MISC package. See the "Making LAMMPS"_Section_start.html#start_3
section for more info on packages.
[Related commands:]
"pair_coeff"_pair_coeff.html
[Default:] none
:line
:link(Mei)
[(Mei)] Mei, Davenport, Fernando, Phys Rev B, 43 4653 (1991)
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