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