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### fix store/state command

Syntax:

    fix ID group-ID store/state N input1 input2 ... keyword value ...

- ID, group-ID are documented in fix command
- store/state = style name of this fix command
- N = store atom attributes every N steps, N = 0 for initial store only
- input = one or more atom attributes

        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, tqx, tqy, tqz
      			c_ID, c_ID[N], f_ID, f_ID[N], v_name

            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
            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

- zero or more keyword/value pairs may be appended
- keyword = com

        com value = yes or no

Examples:

    fix 1 all store/state 0 x y z
    fix 1 all store/state 0 xu yu zu com yes
    fix 2 all store/state 1000 vx vy vz

Description:

Define a fix that stores attributes for each atom in the group at the time the fix is defined. If N 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 output commands that take fixes as inputs. And see for example, the compute reduce, fix ave/atom, fix ave/histo, fix ave/spatial, and atom-style variable commands.

If N is not zero, then the attributes will be updated every N steps.

IMPORTANT NOTE: Actually, only atom attributes specified by keywords like xu or vy 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.

The list of possible attributes is the same as that used by the dump custom command, which describes their meaning.

If the com keyword is set to yes then the xu, yu, and zu 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 compute msd command.

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.

Restart, fix_modify, output, run start/stop, minimize info:

This fix writes the per-atom values it stores to binary restart files, so that the values can be restored when a simulation is restarted. See the read_restart 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.

None of the fix_modify options are relevant to this fix.

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 output commands. The per-atom values be accessed on any timestep.

No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

Restrictions: none

Related commands:

dump custom, compute property/atom, variable

Default:

The option default is com = no.