forked from lijiext/lammps
128 lines
4.8 KiB
Plaintext
128 lines
4.8 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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fix store/state command :h3
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[Syntax:]
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fix ID group-ID store/state N input1 input2 ... keyword value ... :pre
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ID, group-ID are documented in "fix"_fix.html command :ulb,l
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store/state = style name of this fix command :l
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N = store atom attributes every N steps, N = 0 for initial store only :l
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input = one or more atom attributes :l
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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, tqx, tqy, tqz
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c_ID, c_ID\[N\], f_ID, f_ID\[N\], v_name :pre
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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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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 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 :pre
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zero or more keyword/value pairs may be appended :l
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keyword = {com} :l
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{com} value = {yes} or {no} :pre
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:ule
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[Examples:]
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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 :pre
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[Description:]
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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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"output commands"_Section_howto.html#howto_15 that take fixes as
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inputs. And see for example, the "compute
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reduce"_compute_reduce.html, "fix ave/atom"_fix_ave_atom.html, "fix
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ave/histo"_fix_ave_histo.html, "fix ave/spatial"_fix_ave_spatial.html,
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and "atom-style variable"_variable.html commands.
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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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IMPORTANT NOTE: Actually, only atom attributes specified by keywords
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like {xu} or {vy} 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 "dump
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custom"_dump.html 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. This
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option is used by the "compute msd"_compute_msd.html command.
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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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This fix writes the per-atom values it stores to "binary restart
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files"_restart.html, so that the values can be restored when a
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simulation is restarted. See the "read_restart"_read_restart.html
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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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None of the "fix_modify"_fix_modify.html 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 "output
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commands"_Section_howto.html#howto_15. The per-atom values be
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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 "run"_run.html command. This fix is not invoked during "energy
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minimization"_minimize.html.
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[Restrictions:] none
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[Related commands:]
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"dump custom"_dump.html, "compute
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property/atom"_compute_property_atom.html, "variable"_variable.html
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[Default:]
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The option default is com = no.
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