Page Menu
Home
c4science
Search
Configure Global Search
Log In
Files
F92819597
compute_stress_atom.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, 23:08
Size
2 KB
Mime Type
text/html
Expires
Mon, Nov 25, 23:08 (1 d, 15 h)
Engine
blob
Format
Raw Data
Handle
22453971
Attached To
rLAMMPS lammps
compute_stress_atom.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>
compute stress/atom command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
compute ID group-ID stress/atom
</PRE>
<UL><LI>
ID, group-ID are documented in
<A
HREF =
"compute.html"
>
compute
</A>
command
<LI>
stress/atom = style name of this compute command
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
compute 1 mobile stress/atom
</PRE>
<P><B>
Description:
</B>
</P>
<P>
Define a computation that computes the per-atom stress tensor for each
atom in a group. The 6 components can be output via the
<A
HREF =
"dump.html"
>
dump
custom
</A>
command.
</P>
<P>
The stress tensor is computed for only pairwise forces where the
<I>
ab
</I>
component of stress on atom
<I>
i
</I>
is given by
</P>
<CENTER><IMG
SRC =
"Eqs/stress_tensor.jpg"
>
</CENTER>
<P>
where the first term is a kinetic energy component for atom
<I>
i
</I>
,
<I>
j
</I>
loops over the
<I>
N
</I>
neighbors of atom
<I>
i
</I>
, and
<I>
Fb
</I>
is one of 3
components of force on atom
<I>
i
</I>
due to atom
<I>
j
</I>
. Both
<I>
a
</I>
and
<I>
b
</I>
take on values x,y,z to generate the 6 components of the symmetric
tensor.
</P>
<P>
Note that this formula for stress does not include virial
contributions from intra-molecular interactions (e.g. bonds, angles,
torsions, etc). Also note that this quantity is the negative of the
per-atom pressure tensor. It is also really a stress-volume
formulation. It would need to be divided by a per-atom volume to have
units of stress, but an individual atom's volume is not easy to
compute in a deformed solid. Thus, if you sum the diagonal components
of the per-atom stress tensor for all atoms in the system and divide
the sum by 3V, where V is the volume of the system, you should get -P,
where P is the total pressure of the system.
</P>
<P>
Computation of per-atom stress tensor components requires a loop thru
the neighbor list and inter-processor communication, so it can be
inefficient to compute/dump this quantity too frequently or to have
multiple compute/dump commands, each of a
<I>
stress/atom
</I>
style.
</P>
<P><B>
Restrictions:
</B>
none
</P>
<P><B>
Related commands:
</B>
none
</P>
<P><B>
Default:
</B>
none
</P>
</HTML>
Event Timeline
Log In to Comment