154 lines
5.7 KiB
ReStructuredText
154 lines
5.7 KiB
ReStructuredText
.. index:: fix store/state
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fix store/state command
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=======================
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Syntax
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""""""
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.. code-block:: LAMMPS
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fix ID group-ID store/state N input1 input2 ... keyword value ...
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* ID, group-ID are documented in :doc:`fix <fix>` command
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* store/state = style name of this fix command
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* N = store atom attributes every N steps, N = 0 for initial store only
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* input = one or more atom attributes
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.. parsed-literal::
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possible attributes = id, mol, type, mass,
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x, y, z, xs, ys, zs, xu, yu, zu, xsu, ysu, zsu, ix, iy, iz,
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vx, vy, vz, fx, fy, fz,
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q, mux, muy, muz, mu,
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radius, diameter, omegax, omegay, omegaz,
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angmomx, angmomy, angmomz, tqx, tqy, tqz,
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c_ID, c_ID[I], f_ID, f_ID[I], v_name,
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d_name, i_name, i2_name[I], d2_name[I],
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.. parsed-literal::
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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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xsu,ysu,zsu = scaled 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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mu = magnitued of dipole moment of atom
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radius,diameter = radius.diameter of spherical particle
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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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tqx,tqy,tqz = torque on finite-size 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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*i_name* = custom integer vector with name
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*d_name* = custom floating point vector with name
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*i2_name[I]* = Ith column of custom integer array with name
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*d2_name[I]* = Ith column of custom floating-point array with name
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* zero or more keyword/value pairs may be appended
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* keyword = *com*
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.. parsed-literal::
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*com* value = *yes* or *no*
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Examples
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""""""""
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.. code-block:: LAMMPS
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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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Description
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"""""""""""
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Define a fix that stores attributes for each atom in the group at the
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time the fix is defined. If *N* 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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:doc:`output commands <Howto_output>` that take fixes as inputs.
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If *N* is not zero, then the attributes will be updated every *N*
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steps.
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.. note::
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Actually, only atom attributes specified by keywords like *xu*
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or *vy* or *radius* 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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The list of possible attributes is the same as that used by the
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:doc:`dump custom <dump>` command, which describes their meaning.
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If the *com* keyword is set to *yes* then the *xu*, *yu*, and *zu*
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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.
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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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Restart, fix_modify, output, run start/stop, minimize info
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"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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This fix writes the per-atom values it stores to :doc:`binary restart
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files <restart>`, so that the values can be restored when a simulation
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is restarted. See the :doc:`read_restart <read_restart>` command for
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info on how to re-specify a fix in an input script that reads a
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restart file, so that the operation of the fix continues in an
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uninterrupted fashion.
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.. warning::
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When reading data from a restart file, this fix command has to be specified
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**exactly** the same way as before. LAMMPS will only check whether a
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fix is of the same style and has the same fix ID and in case of a match
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will then try to initialize the fix with the data stored in the binary
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restart file. If the fix store/state command does not match exactly,
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data can be corrupted or LAMMPS may crash.
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None of the :doc:`fix_modify <fix_modify>` options are relevant to this
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fix.
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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 :doc:`output commands <Howto_output>`. The
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per-atom values be accessed on any timestep.
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No parameter of this fix can be used with the *start/stop* keywords of
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the :doc:`run <run>` command. This fix is not invoked during
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:doc:`energy minimization <minimize>`.
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Restrictions
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""""""""""""
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none
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Related commands
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""""""""""""""""
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:doc:`dump custom <dump>`, :doc:`compute property/atom <compute_property_atom>`,
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:doc:`fix property/atom <fix_property_atom>`, :doc:`variable <variable>`
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Default
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"""""""
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The option default is com = no.
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