2007-02-10 05:40:32 +08:00
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"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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2007-02-21 08:18:01 +08:00
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compute centro/atom command :h3
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2007-02-10 05:40:32 +08:00
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[Syntax:]
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2007-02-21 08:18:01 +08:00
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compute ID group-ID centro/atom :pre
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2007-02-10 05:40:32 +08:00
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ID, group-ID are documented in "compute"_compute.html command
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2007-02-21 08:18:01 +08:00
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centro/atom = style name of this compute command :ul
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2007-02-10 05:40:32 +08:00
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[Examples:]
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2007-02-21 08:18:01 +08:00
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compute 1 all centro/atom :pre
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2007-02-10 05:40:32 +08:00
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[Description:]
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Define a computation that calculates the centro-symmetry parameter for
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2009-01-20 01:17:01 +08:00
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each atom in the group. In solid-state systems the centro-symmetry
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2007-07-03 03:59:42 +08:00
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parameter is a useful measure of the local lattice disorder around an
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atom and can be used to characterize whether the atom is part of a
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perfect lattice, a local defect (e.g. a dislocation or stacking
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fault), or at a surface.
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2007-02-10 05:40:32 +08:00
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2007-11-20 23:37:16 +08:00
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The value of the centro-symmetry parameter will be 0.0 for atoms not
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in the specified compute group.
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2007-02-10 05:40:32 +08:00
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This parameter is computed using the following formula from
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"(Kelchner)"_#Kelchner
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:c,image(Eqs/centro_symmetry.jpg)
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2008-04-07 23:58:34 +08:00
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where the 12 nearest neighbors are found (for fcc lattices) and Ri and
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Ri+6 are the vectors from the central atom to the opposite pair of
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nearest neighbors. Atoms not in the group are included in the 12
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neighbors used in this calculation.
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2007-02-10 05:40:32 +08:00
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The neighbor list needed to compute this quantity is constructed each
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2009-01-20 01:17:01 +08:00
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time the calculation is performed (e.g. each time a snapshot of atoms
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2007-02-10 05:40:32 +08:00
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is dumped). Thus it can be inefficient to compute/dump this quantity
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2009-01-20 01:17:01 +08:00
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too frequently or to have multiple compute/dump commands, each with a
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2007-02-10 05:40:32 +08:00
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{centro/atom} style.
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2008-01-04 08:56:10 +08:00
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[Output info:]
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This compute calculates a scalar quantity for each atom, which can be
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accessed by any command that uses per-atom computes as input. See
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"this section"_Section_howto.html#4_15 for an overview of LAMMPS
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output options.
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2007-02-10 05:40:32 +08:00
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[Restrictions:] none
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2009-01-20 01:17:01 +08:00
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[Related commands:]
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"compute cna/atom"_compute_cna_atom.html
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2007-02-10 05:40:32 +08:00
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[Default:] none
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:line
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:link(Kelchner)
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[(Kelchner)] Kelchner, Plimpton, Hamilton, Phys Rev B, 58, 11085 (1998).
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