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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>
</CENTER>
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<H3>fix store command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID store N input1 input2 ... keyword value ...
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
<LI>store= style name of this fix command
<LI>N = store atom attributes every N steps, N = 0 for initial store only
<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,
radius, omegax, omegay, omegaz,
angmomx, angmomy, angmomz,
quatw, quati, quatj, quatk, tqx, tqy, tqz
c_ID, c_ID[N], f_ID, f_ID[N], v_name
</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 dipolar atom
radius = radius of extended spherical particle
omegax,omegay,omegaz = angular velocity of extended particle
angmomx,angmomy,angmomz = angular momentum of extended particle
quatw,quati,quatj,quatk = quaternion components for aspherical particles
tqx,tqy,tqz = torque on extended particles
c_ID = per-atom vector calculated by a compute with ID
c_ID[I] = Ith column of per-atom array calculated by a compute with ID
f_ID = per-atom vector calculated by a fix with ID
f_ID[I] = Ith column of per-atom array calculated by a fix with ID
v_name = per-atom vector calculated by an atom-style variable with name
</PRE>
<LI>zero or more keyword/value pairs may be appended
<LI>keyword = <I>com</I>
<PRE> <I>com</I> value = <I>yes</I> or <I>no</I>
</PRE>
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix 1 all store 0 x y z
fix 1 all store 0 xu yu zu com yes
fix 2 all store 1000 vx vy vz
</PRE>
<P><B>Description:</B>
</P>
<P>Define a fix that stores attributes for each atom in the group at the
time the fix is defined. If <I>N</I> is 0, then the values are never
updated, so this is a way of archiving an atom attribute at a given
time for future use in a calculation or output. See the discussion of
<A HREF = "Section_howto.html#4_15">output commands</A> that take fixes as inputs.
And 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>If <I>N</I> is not zero, then the attributes will be updated every <I>N</I>
steps.
</P>
<P>IMPORTANT NOTE: Actually, only atom attributes specified by keywords
like <I>xu</I> or <I>vy</I> are initially stored immediately at the point in
your input script when the fix is defined. Attributes specified by a
compute, fix, or variable are not initially stored until the first run
following the fix definition begins. This is because calculating
those attributes may require quantities that are not defined in
between runs.
</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.
</P>
<P>If the <I>com</I> keyword is set to <I>yes</I> then the <I>xu</I>, <I>yu</I>, and <I>zu</I>
inputs store the position of each atom relative to the center-of-mass
of the group of atoms, instead of storing the absolute position. This
option is used by the <A HREF = "compute_msd.html">compute msd</A> command.
</P>
<P>The requested values are stored in a per-atom vector or array as
discussed below. Zeroes are stored for atoms not in the specified
group.
</P>
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
</P>
<P>This fix writes the per-atom values it stores to <A HREF = "restart.html">binary restart
files</A>, so that the values can be restored when a
simulation is restarted. See the <A HREF = "read_restart.html">read_restart</A>
command for info on how to re-specify a fix in an input script that
reads a restart file, so that the operation of the fix continues in an
uninterrupted fashion.
</P>
<P>None of the <A HREF = "fix_modify.html">fix_modify</A> options are relevant to this
fix.
</P>
<P>If a single input is specified, this fix produces a per-atom vector.
If multiple inputs are specified, a per-atom array is produced where
the number of columns for each atom is the number of inputs. These
can be accessed by various <A HREF = "Section_howto.html#4_15">output commands</A>.
The per-atom values be accessed on any timestep.
</P>
<P>No parameter of this fix can be used with the <I>start/stop</I> keywords of
the <A HREF = "run.html">run</A> command. This fix is not invoked during <A HREF = "minimize.html">energy
minimization</A>.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "dump.html">dump custom</A>, <A HREF = "compute_property_atom.html">compute
property/atom</A>, <A HREF = "variable.html">variable</A>
</P>
<P><B>Default:</B>
</P>
<P>The option default is com = no.
</P>
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