Page Menu
Home
c4science
Search
Configure Global Search
Log In
Files
F92804633
pair_yukawa_colloid.html
No One
Temporary
Actions
Download File
Edit File
Delete File
View Transforms
Subscribe
Mute Notifications
Award Token
Subscribers
None
File Metadata
Details
File Info
Storage
Attached
Created
Sat, Nov 23, 20:46
Size
6 KB
Mime Type
text/html
Expires
Mon, Nov 25, 20:46 (1 d, 21 h)
Engine
blob
Format
Raw Data
Handle
22517048
Attached To
rLAMMPS lammps
pair_yukawa_colloid.html
View Options
<HTML>
<CENTER><A
HREF =
"http://lammps.sandia.gov"
>
LAMMPS WWW Site
</A>
-
<A
HREF =
"Manual.html"
>
LAMMPS Documentation
</A>
-
<A
HREF =
"Section_commands.html#comm"
>
LAMMPS Commands
</A>
</CENTER>
<HR>
<H3>
pair_style yukawa/colloid command
</H3>
<H3>
pair_style yukawa/colloid/gpu command
</H3>
<H3>
pair_style yukawa/colloid/omp command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
pair_style yukawa/colloid kappa cutoff
</PRE>
<UL><LI>
kappa = screening length (inverse distance units)
<LI>
cutoff = global cutoff for colloidal Yukawa interactions (distance units)
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
pair_style yukawa/colloid 2.0 2.5
pair_coeff 1 1 100.0 2.3
pair_coeff * * 100.0
</PRE>
<P><B>
Description:
</B>
</P>
<P>
Style
<I>
yukawa/colloid
</I>
computes pairwise interactions with the formula
</P>
<CENTER><IMG
SRC =
"Eqs/pair_yukawa_colloid.jpg"
>
</CENTER>
<P>
where Ri and Rj are the radii of the two particles and Rc is the
cutoff.
</P>
<P>
In contrast to
<A
HREF =
"pair_yukawa.html"
>
pair_style yukawa
</A>
, this functional
form arises from the Coulombic interaction between two colloid
particles, screened due to the presence of an electrolyte, see the
book by
<A
HREF =
"#Safran"
>
Safran
</A>
for a derivation in the context of DVLO
theory.
<A
HREF =
"pair_yukawa.html"
>
Pair_style yukawa
</A>
is a screened Coulombic
potential between two point-charges and uses no such approximation.
</P>
<P>
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
.
</
P
>
<P>
When used in combination with
<A
HREF =
"pair_colloid.html"
>
pair_style colloid
</A>
,
the two terms become the so-called DLVO potential, which combines
electrostatic repulsion and van der Waals attraction.
</P>
<P>
The following coefficients must be defined for each pair of atoms
types via the
<A
HREF =
"pair_coeff.html"
>
pair_coeff
</A>
command as in the examples
above, or in the data file or restart files read by the
<A
HREF =
"read_data.html"
>
read_data
</A>
or
<A
HREF =
"read_restart.html"
>
read_restart
</A>
commands, or by mixing as described below:
</P>
<UL><LI>
A (energy/distance units)
<LI>
cutoff (distance units)
</UL>
<P>
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
<A
HREF =
"pair_yukawa.html"
>
pair_style yukawa
</A>
. For low surface
potentials, i.e. less than about 25 mV, A can be written as:
</P>
<PRE>
A = 2 * PI * R*eps*eps0 * kappa * psi^2
</PRE>
<P>
where
</P>
<UL><LI>
R = colloid radius (distance units)
<LI>
eps0 = permittivity of free space (charge^2/energy/distance units)
<LI>
eps = relative permittivity of fluid medium (dimensionless)
<LI>
kappa = inverse screening length (1/distance units)
<LI>
psi = surface potential (energy/charge units)
</UL>
<P>
The last coefficient is optional. If not specified, the global
yukawa/colloid cutoff is used.
</P>
<HR>
<P>
Styles with a
<I>
cuda
</I>
,
<I>
gpu
</I>
,
<I>
intel
</I>
,
<I>
kk
</I>
,
<I>
omp
</I>
, or
<I>
opt
</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
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, GPU, USER-INTEL,
KOKKOS, USER-OMP and OPT packages, respectively. They are only
enabled if LAMMPS was built with those packages. 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>
Mixing, shift, table, tail correction, restart, rRESPA info
</B>
:
</P>
<P>
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
<I>
geometric
</I>
. See the
"pair_modify" command for details.
</P>
<P>
This pair style supports the
<A
HREF =
"pair_modify.html"
>
pair_modify
</A>
shift
option for the energy of the pair interaction.
</P>
<P>
The
<A
HREF =
"pair_modify.html"
>
pair_modify
</A>
table option is not relevant
for this pair style.
</P>
<P>
This pair style does not support the
<A
HREF =
"pair_modify.html"
>
pair_modify
</A>
tail option for adding long-range tail corrections to energy and
pressure.
</P>
<P>
This pair style writes its information to
<A
HREF =
"restart.html"
>
binary restart
files
</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>
This pair style can only be used via the
<I>
pair
</I>
keyword of the
<A
HREF =
"run_style.html"
>
run_style respa
</A>
command. It does not support the
<I>
inner
</I>
,
<I>
middle
</I>
,
<I>
outer
</I>
keywords.
</P>
<HR>
<P><B>
Restrictions:
</B>
</P>
<P>
This style is part of the COLLOID package. It is 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>
This pair style requires that atoms be finite-size spheres with a
diameter, as defined by the
<A
HREF =
"atom_style.html"
>
atom_style sphere
</A>
command.
</P>
<P>
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.
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"pair_coeff.html"
>
pair_coeff
</A>
</P>
<P><B>
Default:
</B>
none
</P>
<HR>
<A
NAME =
"Safran"
></A>
<P><B>
(Safran)
</B>
Safran, Statistical Thermodynamics of Surfaces, Interfaces,
And Membranes, Westview Press, ISBN: 978-0813340791 (2003).
</P>
</HTML>
Event Timeline
Log In to Comment