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compute_property_atom.html
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rLAMMPS lammps
compute_property_atom.html
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<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 property/atom command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
compute ID group-ID property/atom input1 input2 ...
</PRE>
<UL><LI>
ID, group-ID are documented in
<A
HREF =
"compute.html"
>
compute
</A>
command
<LI>
property/atom = style name of this compute command
<LI>
input = one or more atom attributes
<PRE>
possible attributes = id, mol, type, mass,
x, y, z, xs, ys, zs, xu, yu, zu, ix, iy, iz,
vx, vy, vz, fx, fy, fz,
q, mux, muy, muz, mu,
radius, diameter, omegax, omegay, omegaz,
angmomx, angmomy, angmomz,
shapex,shapey, shapez,
quatw, quati, quatj, quatk, tqx, tqy, tqz,
spin, eradius, ervel, erforce
end1x, end1y, end1z, end2x, end2y, end2z,
corner1x, corner1y, corner1z,
corner2x, corner2y, corner2z,
corner3x, corner3y, corner3z
</PRE>
<PRE>
id = atom ID
mol = molecule ID
type = atom type
mass = atom mass
x,y,z = unscaled atom coordinates
xs,ys,zs = scaled atom coordinates
xu,yu,zu = unwrapped atom coordinates
ix,iy,iz = box image that the atom is in
vx,vy,vz = atom velocities
fx,fy,fz = forces on atoms
q = atom charge
mux,muy,muz = orientation of dipole moment of atom
mu = magnitude of dipole moment of atom
radius,diameter = radius,diameter of spherical particle
omegax,omegay,omegaz = angular velocity of extended particle
angmomx,angmomy,angmomz = angular momentum of extended particle
shapex,shapey,shapez = 3 diameters of aspherical particle
quatw,quati,quatj,quatk = quaternion components for aspherical particles
tqx,tqy,tqz = torque on extended particles
spin = electron spin
eradius = electron radius
ervel = electron radial velocity
erforce = electron radial force
end12x, end12y, end12z = end points of line segment
coner123x, corner123y, corner123z = corner points of triangle
</PRE>
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
compute 1 all property/atom xs vx fx mux
compute 2 all property/atom type
compute 1 all property/atom ix iy iz
</PRE>
<P><B>
Description:
</B>
</P>
<P>
Define a computation that simply stores atom attributes for each atom
in the group. This is useful so that the values can be used by other
<A
HREF =
"Section_howto.html#howto_15"
>
output commands
</A>
that take computes as
inputs. See for example, the
<A
HREF =
"compute_reduce.html"
>
compute reduce
</A>
,
<A
HREF =
"fix_ave_atom.html"
>
fix ave/atom
</A>
,
<A
HREF =
"fix_ave_histo.html"
>
fix ave/histo
</A>
,
<A
HREF =
"fix_ave_spatial.html"
>
fix ave/spatial
</A>
, and
<A
HREF =
"variable.html"
>
atom-style
variable
</A>
commands.
</P>
<P>
The list of possible attributes is the same as that used by the
<A
HREF =
"dump.html"
>
dump
custom
</A>
command, which describes their meaning, with some
additional quantities that are only defined for certain
<A
HREF =
"atom_style.html"
>
atom
styles
</A>
. Basically, this list gives your input script
access to any per-atom quantity stored by LAMMPS.
</P>
<P>
The values are stored in a per-atom vector or array as discussed
below. Zeroes are stored for atoms not in the specified group or for
quantities that are not defined for a particular particle in the group
(e.g.
<I>
shapex
</I>
if the particle is not an ellipsoid).
</P>
<P>
The additional quantities only accessible via this command, and not
directly via the
<A
HREF =
"dump.html"
>
dump custom
</A>
command, are as follows.
</P>
<P><I>
Shapex
</I>
,
<I>
shapey
</I>
, and
<I>
shapez
</I>
are defined for ellipsoidal particles
and define the 3d shape of each particle.
<I>
Quatw
</I>
,
<I>
quati
</I>
,
<I>
quatj
</I>
,
and
<I>
quatk
</I>
are also defined for ellipsoidal particles and store the
4-vector quaternion representing the orientation of each particle.
See the
<A
HREF =
"set.html"
>
set
</A>
command for an explanation of the quaternion
vector.
</P>
<P><I>
End1x
</I>
,
<I>
end1y
</I>
,
<I>
end1z
</I>
,
<I>
end2x
</I>
,
<I>
end2y
</I>
,
<I>
end2z
</I>
, are defined for
line segment particles and define the end points of each line segment.
</P>
<P><I>
Corner1x
</I>
,
<I>
corner1y
</I>
,
<I>
corner1z
</I>
,
<I>
corner2x
</I>
,
<I>
corner2y
</I>
,
<I>
corner2z
</I>
,
<I>
corner3x
</I>
,
<I>
corner3y
</I>
,
<I>
corner3z
</I>
, are defined for
triangular particles and define the corner points of each triangle.
</P>
<P><B>
Output info:
</B>
</P>
<P>
This compute calculates a per-atom vector or per-atom array depending
on the number of input values. If a single input is specified, a
per-atom vector is produced. If two or more inputs are specified, a
per-atom array is produced where the number of columns = the number of
inputs. The vector or array can be accessed by any command that uses
per-atom values from a compute as input. See
<A
HREF =
"Section_howto.html#howto_15"
>
this
section
</A>
for an overview of LAMMPS output
options.
</P>
<P>
The vector or array values will be in whatever
<A
HREF =
"units.html"
>
units
</A>
the
corresponding attribute is in, e.g. velocity units for vx, charge
units for q, etc.
</P>
<P><B>
Restrictions:
</B>
none
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"dump.html"
>
dump custom
</A>
,
<A
HREF =
"compute_reduce.html"
>
compute reduce
</A>
,
<A
HREF =
"fix_ave_atom.html"
>
fix
ave/atom
</A>
,
<A
HREF =
"fix_ave_spatial.html"
>
fix ave/spatial
</A>
</P>
<P><B>
Default:
</B>
none
</P>
</HTML>
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