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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2014-07-23 06:52:19 +08:00
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<PRE> possible attributes = id, mol, proc, type, mass,
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2009-12-17 01:12:09 +08:00
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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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2011-10-20 23:01:56 +08:00
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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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2013-07-26 04:59:36 +08:00
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corner3x, corner3y, corner3z,
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2014-05-03 05:47:08 +08:00
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nbonds,
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2014-06-05 07:04:09 +08:00
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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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2013-07-26 04:59:36 +08:00
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i_name, d_name
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2009-12-18 01:28:42 +08:00
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</PRE>
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2014-06-05 05:31:27 +08:00
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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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2014-07-23 06:52:19 +08:00
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proc = ID of processor that owns atom
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2009-12-17 01:12:09 +08:00
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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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2013-02-01 03:46:51 +08:00
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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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2011-10-20 23:01:56 +08:00
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shapex,shapey,shapez = 3 diameters of aspherical particle
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2013-02-01 01:24:45 +08:00
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quatw,quati,quatj,quatk = quaternion components for aspherical or body particles
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2013-02-01 03:46:51 +08:00
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tqx,tqy,tqz = torque on finite-size particles
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2014-06-05 05:27:34 +08:00
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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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2014-11-18 02:40:51 +08:00
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nbonds = number of bonds assigned to an atom
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2014-06-05 05:31:27 +08:00
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</PRE>
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<PRE> PERI package per-atom properties:
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2014-06-05 05:27:34 +08:00
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vfrac = ???
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2014-06-05 05:31:27 +08:00
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s0 = ???
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</PRE>
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<PRE> USER-EFF and USER-AWPMD package per-atom properties:
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2010-08-21 07:17:55 +08:00
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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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2014-06-05 05:31:27 +08:00
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erforce = electron radial force
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</PRE>
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<PRE> USER-SPH package per-atom properties:
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2014-06-05 05:27:34 +08:00
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rho = ???
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drho = ???
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e = ???
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de = ???
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2014-06-05 05:31:27 +08:00
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cv = ???
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</PRE>
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2014-06-05 05:27:34 +08:00
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<PRE> <A HREF = "fix_property_atom.html">fix property/atom</A> per-atom properties:
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2013-07-26 04:59:36 +08:00
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i_name = custom integer vector with name
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d_name = custom integer vector with name
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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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2011-08-26 01:01:01 +08:00
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<A HREF = "Section_howto.html#howto_15">output commands</A> that take computes as
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2009-12-17 01:12:09 +08:00
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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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2014-07-23 06:52:19 +08:00
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styles</A>. 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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2009-12-17 01:12:09 +08:00
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</P>
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2011-10-20 06:43:40 +08:00
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<P>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. <I>shapex</I> if the particle is not an ellipsoid).
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2009-12-17 01:12:09 +08:00
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</P>
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2011-10-20 06:43:40 +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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2011-05-30 23:46:25 +08:00
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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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2013-02-01 01:24:45 +08:00
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and define the 3d shape of each particle.
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</P>
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<P><I>Quatw</I>, <I>quati</I>, <I>quatj</I>, and <I>quatk</I> 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 <A HREF = "set.html">set</A>
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command for an explanation of the quaternion vector.
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2011-05-30 23:46:25 +08:00
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</P>
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2011-10-20 23:01:56 +08:00
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<P><I>End1x</I>, <I>end1y</I>, <I>end1z</I>, <I>end2x</I>, <I>end2y</I>, <I>end2z</I>, are defined for
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line segment particles and define the end points of each line segment.
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</P>
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<P><I>Corner1x</I>, <I>corner1y</I>, <I>corner1z</I>, <I>corner2x</I>, <I>corner2y</I>,
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<I>corner2z</I>, <I>corner3x</I>, <I>corner3y</I>, <I>corner3z</I>, are defined for
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triangular particles and define the corner points of each triangle.
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</P>
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2014-11-18 02:40:51 +08:00
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<P><I>Nbonds</I> 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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<A HREF = "newton.html">newton bond</A> command is set to <I>on</I>, 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 <A HREF = "newton.html">newton bond off</A> is set,
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it will be tallied with both atom I and atom J.
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2014-05-03 05:47:08 +08:00
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</P>
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2013-07-26 04:59:36 +08:00
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<P>The <I>i_name</I> and <I>d_name</I> 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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<A HREF = "fix_property_atom.html">fix property/atom</A> 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>i_name</I> or <I>d_name</I>.
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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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2011-08-26 01:01:01 +08:00
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per-atom values from a compute as input. See <A HREF = "Section_howto.html#howto_15">this
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2009-12-17 01:12:09 +08:00
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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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2013-07-26 04:59:36 +08:00
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ave/atom</A>, <A HREF = "fix_ave_spatial.html">fix ave/spatial</A>,
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<A HREF = "fix_property_atom.html">fix property/atom</A>
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2009-12-17 01:12:09 +08:00
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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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