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lammps/doc/pair_yukawa_colloid.txt
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pair_yukawa_colloid.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 yukawa/colloid command :h3
pair_style yukawa/colloid/omp command :h3
[Syntax:]
pair_style yukawa/colloid kappa cutoff :pre
kappa = screening length (inverse distance units)
cutoff = global cutoff for colloidal Yukawa interactions (distance units) :ul
[Examples:]
pair_style yukawa/colloid 2.0 2.5
pair_coeff 1 1 100.0 2.3
pair_coeff * * 100.0 :pre
[Description:]
Style {yukawa/colloid} computes pairwise interactions with the formula
:c,image(Eqs/pair_yukawa_colloid.jpg)
where Ri and Rj are the radii of the two particles and Rc is the
cutoff.
In contrast to "pair_style yukawa"_pair_yukawa.html, this functional
form arises from the Coulombic interaction between two colloid
particles, screened due to the presence of an electrolyte.
"Pair_style yukawa"_pair_yukawa.html is a screened Coulombic potential
between two point-charges and uses no such approximation.
This potential applies to nearby particle pairs for which the Derjagin
approximation holds, meaning h << Ri + Rj, where h is the
surface-to-surface separation of the two particles.
When used in combination with "pair_style colloid"_pair_colloid.html,
the two terms become the so-called DLVO potential, which combines
electrostatic repulsion and van der Waals attraction.
The following coefficients must be defined for each pair of atoms
types via the "pair_coeff"_pair_coeff.html 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"_read_restart.html
commands, or by mixing as described below:
A (energy/distance units)
cutoff (distance units) :ul
The prefactor A is determined from the relationship between surface
charge and surface potential due to the presence of electrolyte. Note
that the A for this potential style has different units than the A
used in "pair_style yukawa"_pair_yukawa.html. For low surface
potentials, i.e. less than about 25 mV, A can be written as:
A = 2 * PI * R*eps*eps0 * kappa * psi^2 :pre
where
R = colloid radius (distance units)
eps0 = permittivity of free space (charge^2/energy/distance units)
eps = relative permittivity of fluid medium (dimensionless)
kappa = inverse screening length (1/distance units)
psi = surface potential (energy/charge units) :ul
The last coefficient is optional. If not specified, the global
yukawa/colloid cutoff is used.
:line
Styles with a {cuda}, {gpu}, {omp}, or {opt} 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 "Section_accelerate"_Section_accelerate.html of the
manual. The accelerated styles take the same arguments and should
produce the same results, except for round-off and precision issues.
These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
packages, respectively. They are only enabled if LAMMPS was built with
those packages. See the "Making LAMMPS"_Section_start.html#start_3
section for more info.
You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Section_start.html#start_6 when you invoke LAMMPS, or you can
use the "suffix"_suffix.html command in your input script.
See "Section_accelerate"_Section_accelerate.html of the manual for
more instructions on how to use the accelerated styles effectively.
:line
[Mixing, shift, table, tail correction, restart, rRESPA info]:
For atom type pairs I,J and I != J, the A coefficient and cutoff
distance for this pair style can be mixed. A is an energy value mixed
like a LJ epsilon. The default mix value is {geometric}. See the
"pair_modify" command for details.
This pair style supports the "pair_modify"_pair_modify.html shift
option for the energy of the pair interaction.
The "pair_modify"_pair_modify.html table option is not relevant
for this pair style.
This pair style does not support the "pair_modify"_pair_modify.html
tail option for adding long-range tail corrections to energy and
pressure.
This pair style writes its 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.
This pair style can only be used via the {pair} keyword of the
"run_style respa"_run_style.html command. It does not support the
{inner}, {middle}, {outer} keywords.
:line
[Restrictions:]
This style is part of the COLLOID package. It is only enabled if
LAMMPS was built with that package. See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.
This pair style requires that atoms be finite-size spheres with a
diameter, as defined by the "atom_style sphere"_atom_style.html
command.
Per-particle polydispersity is not yet supported by this pair style;
per-type polydispersity is allowed. This means all particles of the
same type must have the same diameter. Each type can have a different
diameter.
[Related commands:]
"pair_coeff"_pair_coeff.html
[Default:] none
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