2009-12-17 01:12:09 +08:00
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<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>
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<HR>
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<H3>compute property/atom command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>compute ID group-ID property/atom input1 input2 ...
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
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<LI>property/atom = style name of this compute command
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<LI>input = one or more atom attributes
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<PRE> possible attributes = id, mol, 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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2011-04-14 05:39:34 +08:00
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q, mux, muy, muz, mu,
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2011-05-30 23:46:25 +08:00
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radius, diameter, omegax, omegay, omegaz,
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2011-04-14 05:39:34 +08:00
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angmomx, angmomy, angmomz,
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shapex,shapey, shapez,
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2010-08-21 07:17:55 +08:00
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quatw, quati, quatj, quatk, tqx, tqy, tqz,
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2010-08-25 23:35:46 +08:00
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spin, eradius, ervel, erforce
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2009-12-18 01:28:42 +08:00
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</PRE>
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<PRE> id = atom ID
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2009-12-17 01:12:09 +08:00
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mol = molecule ID
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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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2011-04-14 05:39:34 +08:00
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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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2011-05-30 23:46:25 +08:00
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radius,diameter = radius,diameter of spherical particle
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2009-12-17 01:12:09 +08:00
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omegax,omegay,omegaz = angular velocity of extended particle
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angmomx,angmomy,angmomz = angular momentum of extended particle
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2010-08-21 07:17:55 +08:00
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tqx,tqy,tqz = torque on extended particles
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spin = electron spin
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eradius = electron radius
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2010-08-25 23:35:46 +08:00
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ervel = electron radial velocity
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2011-05-30 23:46:25 +08:00
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erforce = electron radial force
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shapex,shapey,shapez = 3 diameters of aspherical particle
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quatw,quati,quatj,quatk = quaternion components for aspherical particles
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2009-12-17 01:12:09 +08:00
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</PRE>
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>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
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>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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<A HREF = "Section_howto.html#4_15">output commands</A> that take computes as
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inputs. See for example, the <A HREF = "compute_reduce.html">compute reduce</A>,
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<A HREF = "fix_ave_atom.html">fix ave/atom</A>, <A HREF = "fix_ave_histo.html">fix ave/histo</A>,
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<A HREF = "fix_ave_spatial.html">fix ave/spatial</A>, and <A HREF = "variable.html">atom-style
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variable</A> commands.
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</P>
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<P>The list of possible attributes is the same as that used by the <A HREF = "dump.html">dump
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2011-05-30 23:46:25 +08:00
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custom</A> command, which describes their meaning, with some
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additional quantities that are only defined for certain <A HREF = "atom_style.html">atom
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styles</A>. Basically, this list gives your input script
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access to any per-atom quantity stored by LAMMPS.
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2009-12-17 01:12:09 +08:00
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</P>
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<P>The values are stored in a per-atom vector or array as
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discussed below. Zeroes are stored for atoms not in the specified
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group.
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</P>
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2011-05-30 23:46:25 +08:00
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<P>The additional quantities only accessible via this command (and not
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directly via the <A HREF = "dump.html">dump custom</A> command are as follows.
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</P>
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<P><I>Shapex</I>, <I>shapey</I>, and <I>shapez</I> are defined for ellipsoidal particles
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and define the 3d shape of each particle. <I>Quatw</I>, <I>quati</I>, <I>quatj</I>,
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and <I>quatk</I> are also defined for ellipsoidal particles and store the
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4-vector quaternion representing the orientation of each particle.
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See the <A HREF = "set.html">set</A> command for an explanation of the quaternion
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vector.
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</P>
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2009-12-17 01:12:09 +08:00
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<P><B>Output info:</B>
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</P>
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<P>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 <A HREF = "Section_howto.html#4_15">this
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section</A> for an overview of LAMMPS output
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options.
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</P>
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2010-01-24 07:20:05 +08:00
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<P>The vector or array values will be in whatever <A HREF = "units.html">units</A> 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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</P>
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2009-12-17 01:12:09 +08:00
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<P><B>Restrictions:</B> none
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "dump.html">dump custom</A>, <A HREF = "compute_reduce.html">compute reduce</A>, <A HREF = "fix_ave_atom.html">fix
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ave/atom</A>, <A HREF = "fix_ave_spatial.html">fix ave/spatial</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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