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lammps/doc/src/compute_property_atom.txt
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compute_property_atom.txt
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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)
:line
compute property/atom command :h3
[Syntax:]
compute ID group-ID property/atom input1 input2 ... :pre
ID, group-ID are documented in "compute"_compute.html command :ulb,l
property/atom = style name of this compute command :l
input = one or more atom attributes :l
possible attributes = id, mol, proc, 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,
end1x, end1y, end1z, end2x, end2y, end2z,
corner1x, corner1y, corner1z,
corner2x, corner2y, corner2z,
corner3x, corner3y, corner3z,
nbonds,
vfrac, s0,
spin, eradius, ervel, erforce,
rho, drho, e, de, cv,
i_name, d_name :pre
id = atom ID
mol = molecule ID
proc = ID of processor that owns atom
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 spherical particle
angmomx,angmomy,angmomz = angular momentum of aspherical particle
shapex,shapey,shapez = 3 diameters of aspherical particle
quatw,quati,quatj,quatk = quaternion components for aspherical or body particles
tqx,tqy,tqz = torque on finite-size particles
end12x, end12y, end12z = end points of line segment
corner123x, corner123y, corner123z = corner points of triangle
nbonds = number of bonds assigned to an atom :pre
PERI package per-atom properties:
vfrac = ???
s0 = ??? :pre
USER-EFF and USER-AWPMD package per-atom properties:
spin = electron spin
eradius = electron radius
ervel = electron radial velocity
erforce = electron radial force :pre
USER-SPH package per-atom properties:
rho = ???
drho = ???
e = ???
de = ???
cv = ??? :pre
"fix property/atom"_fix_property_atom.html per-atom properties:
i_name = custom integer vector with name
d_name = custom integer vector with name :pre
:ule
[Examples:]
compute 1 all property/atom xs vx fx mux
compute 2 all property/atom type
compute 1 all property/atom ix iy iz :pre
[Description:]
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
"output commands"_Section_howto.html#howto_15 that take computes as
inputs. See for example, the "compute reduce"_compute_reduce.html,
"fix ave/atom"_fix_ave_atom.html, "fix ave/histo"_fix_ave_histo.html,
"fix ave/chunk"_fix_ave_chunk.html, and "atom-style
variable"_variable.html commands.
The list of possible attributes is the same as that used by the "dump
custom"_dump.html command, which describes their meaning, with some
additional quantities that are only defined for certain "atom
styles"_atom_style.html. Basically, this augmented list gives an
input script access to any per-atom quantity stored by LAMMPS.
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. {shapex} if the particle is not an ellipsoid).
The additional quantities only accessible via this command, and not
directly via the "dump custom"_dump.html command, are as follows.
{Shapex}, {shapey}, and {shapez} are defined for ellipsoidal particles
and define the 3d shape of each particle.
{Quatw}, {quati}, {quatj}, and {quatk} are defined for ellipsoidal
particles and body particles and store the 4-vector quaternion
representing the orientation of each particle. See the "set"_set.html
command for an explanation of the quaternion vector.
{End1x}, {end1y}, {end1z}, {end2x}, {end2y}, {end2z}, are defined for
line segment particles and define the end points of each line segment.
{Corner1x}, {corner1y}, {corner1z}, {corner2x}, {corner2y},
{corner2z}, {corner3x}, {corner3y}, {corner3z}, are defined for
triangular particles and define the corner points of each triangle.
{Nbonds} is available for all molecular atom styles and refers to the
number of explicit bonds assigned to an atom. Note that if the
"newton bond"_newton.html command is set to {on}, which is the
default, then every bond in the system is assigned to only one of the
two atoms in the bond. Thus a bond between atoms I,J may be tallied
for either atom I or atom J. If "newton bond off"_newton.html is set,
it will be tallied with both atom I and atom J.
The {i_name} and {d_name} attributes refer to custom integer and
floating-point properties that have been added to each atom via the
"fix property/atom"_fix_property_atom.html command. When that command
is used specific names are given to each attribute which are what is
specified as the "name" portion of {i_name} or {d_name}.
[Output info:]
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 "this
section"_Section_howto.html#howto_15 for an overview of LAMMPS output
options.
The vector or array values will be in whatever "units"_units.html the
corresponding attribute is in, e.g. velocity units for vx, charge
units for q, etc.
[Restrictions:] none
[Related commands:]
"dump custom"_dump.html, "compute reduce"_compute_reduce.html, "fix
ave/atom"_fix_ave_atom.html, "fix ave/chunk"_fix_ave_chunk.html,
"fix property/atom"_fix_property_atom.html
[Default:] none
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