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rLAMMPS lammps
fix_store.html
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<HTML>
<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>
<HR>
<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>
</HTML>
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