86 lines
2.5 KiB
Plaintext
86 lines
2.5 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,Commands_all.html)
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:line
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compute ackland/atom command :h3
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[Syntax:]
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compute ID group-ID ackland/atom keyword/value :pre
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ID, group-ID are documented in "compute"_compute.html command :ulb,l
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ackland/atom = style name of this compute command :l
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zero or more keyword/value pairs may be appended :l
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keyword = {legacy} :l
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{legacy} yes/no = use ({yes}) or do not use ({no}) legacy ackland algorithm implementation :pre
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:ule
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[Examples:]
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compute 1 all ackland/atom
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compute 1 all ackland/atom legacy yes :pre
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[Description:]
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Defines a computation that calculates the local lattice structure
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according to the formulation given in "(Ackland)"_#Ackland.
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Historically, LAMMPS had two, slightly different implementations of
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the algorithm from the paper. With the {legacy} keyword, it is
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possible to switch between the pre-2015 ({legacy yes}) and post-2015
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implementation ({legacy no}). The post-2015 variant is the default.
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In contrast to the "centro-symmetry
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parameter"_compute_centro_atom.html this method is stable against
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temperature boost, because it is based not on the distance between
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particles but the angles. Therefore statistical fluctuations are
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averaged out a little more. A comparison with the Common Neighbor
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Analysis metric is made in the paper.
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The result is a number which is mapped to the following different
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lattice structures:
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0 = UNKNOWN
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1 = BCC
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2 = FCC
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3 = HCP
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4 = ICO :ul
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The neighbor list needed to compute this quantity is constructed each
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time the calculation is performed (i.e. each time a snapshot of atoms
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is dumped). Thus it can be inefficient to compute/dump this quantity
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too frequently or to have multiple compute/dump commands, each of
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which computes this quantity.-
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[Output info:]
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This compute calculates a per-atom vector, which can be accessed by
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any command that uses per-atom values from a compute as input. See
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the "Howto output"_Howto_output.html doc page for an overview of
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LAMMPS output options.
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[Restrictions:]
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This compute is part of the USER-MISC package. It is only enabled if
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LAMMPS was built with that package. See the "Build
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package"_Build_package.html doc page for more info.
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The per-atom vector values will be unitless since they are the
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integers defined above.
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[Related commands:]
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"compute centro/atom"_compute_centro_atom.html
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[Default:]
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The keyword {legacy} defaults to {no}.
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:line
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:link(Ackland)
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[(Ackland)] Ackland, Jones, Phys Rev B, 73, 054104 (2006).
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