Page Menu
Home
c4science
Search
Configure Global Search
Log In
Files
F93293218
fix_append_atoms.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
Wed, Nov 27, 16:49
Size
4 KB
Mime Type
text/html
Expires
Fri, Nov 29, 16:49 (1 d, 23 h)
Engine
blob
Format
Raw Data
Handle
22599157
Attached To
rLAMMPS lammps
fix_append_atoms.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>
fix append/atoms command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
fix ID group-ID append/atoms face ... keyword value ...
</PRE>
<UL><LI>
ID, group-ID are documented in
<A
HREF =
"fix.html"
>
fix
</A>
command
<LI>
append/atoms = style name of this fix command
<LI>
face =
<I>
zhi
</I>
<LI>
zero or more keyword/value pairs may be appended
<LI>
keyword =
<I>
basis
</I>
or
<I>
size
</I>
or
<I>
freq
</I>
or
<I>
temp
</I>
or
<I>
random
</I>
or
<I>
units
</I>
<PRE>
<I>
basis
</I>
values = M itype
M = which basis atom
itype = atom type (1-N) to assign to this basis atom
<I>
size
</I>
args = Lz
Lz = z size of lattice region appended in a single event(distance units)
<I>
freq
</I>
args = freq
freq = the number of timesteps between append events
<I>
temp
</I>
args = target damp seed extent
target = target temperature for the region between zhi-extent and zhi (temperature units)
damp = damping parameter (time units)
seed = random number seed for langevin kicks
extent = extent of thermostated region (distance units)
<I>
random
</I>
args = xmax ymax zmax seed
<I>
xmax
</I>
,
<I>
ymax
</I>
,
<I>
zmax
</I>
= maximum displacement in particular direction (distance units)
<I>
seed
</I>
= random number seed for random displacement
<I>
units
</I>
value =
<I>
lattice
</I>
or
<I>
box
</I>
<I>
lattice
</I>
= the wall position is defined in lattice units
<I>
box
</I>
= the wall position is defined in simulation box units
</PRE>
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
fix 1 all append/atoms zhi size 5.0 freq 295 units lattice
fix 4 all append/atoms zhi size 15.0 freq 5 units box
fix A all append/atoms zhi size 1.0 freq 1000 units lattice
</PRE>
<P><B>
Description:
</B>
</P>
<P>
This fix creates atoms on a lattice, appended on the zhi edge of the
system box. This can be useful when a shock or wave is propagating
from zlo. This allows the system to grow with time to accommodate an
expanding wave. A simulation box must already exist, which is
typically created via the
<A
HREF =
"create_box.html"
>
create_box
</A>
command.
Before using this command, a lattice must also be defined using the
<A
HREF =
"lattice.html"
>
lattice
</A>
command.
</P>
<P>
This fix will automatically freeze atoms on the zhi edge of the
system, so that overlaps are avoided when new atoms are appended.
</P>
<P>
The
<I>
basis
</I>
keyword specifies an atom type that will be assigned to
specific basis atoms as they are created. See the
<A
HREF =
"lattice.html"
>
lattice
</A>
command for specifics on how basis atoms are
defined for the unit cell of the lattice. By default, all created
atoms are assigned type = 1 unless this keyword specifies differently.
</P>
<P>
The
<I>
size
</I>
keyword defines the size in z of the chunk of material to
be added.
</P>
<P>
The
<I>
random
</I>
keyword will give the atoms random displacements around
their lattice points to simulate some initial temperature.
</P>
<P>
The
<I>
temp
</I>
keyword will cause a region to be thermostated with a
Langevin thermostat on the zhi boundary. The size of the region is
measured from zhi and is set with the
<I>
extent
</I>
argument.
</P>
<P>
The
<I>
units
</I>
keyword determines the meaning of the distance units used
to define a wall position, but only when a numeric constant is used.
A
<I>
box
</I>
value selects standard distance units as defined by the
<A
HREF =
"units.html"
>
units
</A>
command, e.g. Angstroms for units = real or metal.
A
<I>
lattice
</I>
value means the distance units are in lattice spacings.
The
<A
HREF =
"lattice.html"
>
lattice
</A>
command must have been previously used to
define the lattice spacings.
</P>
<HR>
<P><B>
Restart, fix_modify, output, run start/stop, minimize info:
</B>
</P>
<P>
No information about this fix is written to
<A
HREF =
"restart.html"
>
binary restart
files
</A>
. None of the
<A
HREF =
"fix_modify.html"
>
fix_modify
</A>
options
are relevant to this fix. No global or per-atom quantities are stored
by this fix for access by various
<A
HREF =
"Section_howto.html#howto_15"
>
output
commands
</A>
. No parameter of this fix can
be used with the
<I>
start/stop
</I>
keywords of the
<A
HREF =
"run.html"
>
run
</A>
command.
This fix is not invoked during
<A
HREF =
"minimize.html"
>
energy minimization
</A>
.
</P>
<P><B>
Restrictions:
</B>
</P>
<P>
This fix style is part of the SHOCK 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>
The boundary on which atoms are added with append/atoms must be
shrink/minimum. The opposite boundary may be any boundary type other
than periodic.
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"fix_wall_piston.html"
>
fix wall/piston
</A>
command
</P>
<P><B>
Default:
</B>
</P>
<P>
The keyword defaults are size = 0.0, freq = 0, units = lattice. All
added atoms are of type 1 unless the basis keyword is used.
</P>
</HTML>
Event Timeline
Log In to Comment