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