Page Menu
Home
c4science
Search
Configure Global Search
Log In
Files
F93930477
angle_dipole.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
Mon, Dec 2, 14:31
Size
4 KB
Mime Type
text/html
Expires
Wed, Dec 4, 14:31 (2 d)
Engine
blob
Format
Raw Data
Handle
22428252
Attached To
rLAMMPS lammps
angle_dipole.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>
angle_style dipole command
</H3>
<H3>
angle_style dipole/omp command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
angle_style dipole
</PRE>
<P><B>
Examples:
</B>
</P>
<PRE>
angle_style dipole
angle_coeff 6 2.1 180.0
</PRE>
<P><B>
Description:
</B>
</P>
<P>
The
<I>
dipole
</I>
angle style is used to control the orientation of a dipolar
atom within a molecule
<A
HREF =
"#Orsi"
>
(Orsi)
</A>
. Specifically, the
<I>
dipole
</I>
angle
style restrains the orientation of a point dipole mu_j (embedded in atom
'j') with respect to a reference (bond) vector r_ij = r_i - r_j, where 'i'
is another atom of the same molecule (typically, 'i' and 'j' are also
covalently bonded).
</P>
<P>
It is convenient to define an angle gamma between the 'free' vector mu_j
and the reference (bond) vector r_ij:
</P>
<CENTER><IMG
SRC =
"Eqs/angle_dipole_gamma.jpg"
>
</CENTER>
<P>
The
<I>
dipole
</I>
angle style uses the potential:
</P>
<CENTER><IMG
SRC =
"Eqs/angle_dipole_potential.jpg"
>
</CENTER>
<P>
where K is a rigidity constant and gamma0 is an equilibrium (reference)
angle.
</P>
<P>
The torque on the dipole can be obtained by differentiating the
potential using the 'chain rule' as in appendix C.3 of
<A
HREF =
"#Allen"
>
(Allen)
</A>
:
</P>
<CENTER><IMG
SRC =
"Eqs/angle_dipole_torque.jpg"
>
</CENTER>
<P>
Example: if gamma0 is set to 0 degrees, the torque generated by
the potential will tend to align the dipole along the reference
direction defined by the (bond) vector r_ij (in other words, mu_j is
restrained to point towards atom 'i').
</P>
<P>
Note that the angle dipole potential does not give rise to any force,
because it does not depend on the distance between i and j (it only
depends on the angle between mu_j and r_ij).
</P>
<P>
The following coefficients must be defined for each angle type via the
<A
HREF =
"angle_coeff.html"
>
angle_coeff
</A>
command as in the example 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:
</P>
<UL><LI>
K (energy)
<LI>
gamma0 (degrees)
</UL>
<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_6"
>
-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>
<P><B>
Restrictions:
</B>
</P>
<P>
This angle style can only be used if LAMMPS was built with the
USER-MISC package. See the
<A
HREF =
"Section_start.html#2_3"
>
Making LAMMPS
</A>
section for more info on packages.
</P>
<P>
IMPORTANT NOTE: In the "Angles" section of the data file, the atom ID
'j' corresponding to the dipole to restrain must come before the atom
ID of the reference atom 'i'. A third atom ID 'k' must also be
provided, although 'k' is just a 'dummy' atom which can be any atom;
it may be useful to choose a convention (e.g., 'k'='i') and adhere to
it. For example, if ID=1 for the dipolar atom to restrain, and ID=2
for the reference atom, the corresponding line in the "Angles" section
of the data file would read: X X 1 2 2
</P>
<P>
The "newton" command for intramolecular interactions must be "on"
(which is the default).
</P>
<P>
This angle style should not be used with SHAKE.
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"angle_coeff.html"
>
angle_coeff
</A>
,
<A
HREF =
"angle_hybrid.html"
>
angle_hybrid
</A>
</P>
<P><B>
Default:
</B>
none
</P>
<HR>
<A
NAME =
"Orsi"
></A>
<P><B>
(Orsi)
</B>
Orsi
&
Essex, The ELBA force field for coarse-grain modeling of
lipid membranes, PloS ONE 6(12): e28637, 2011.
</P>
<A
NAME =
"Allen"
></A>
<P><B>
(Allen)
</B>
Allen
&
Tildesley, Computer Simulation of Liquids,
Clarendon Press, Oxford, 1987.
</P>
</HTML>
Event Timeline
Log In to Comment