forked from lijiext/lammps
89 lines
3.2 KiB
Plaintext
89 lines
3.2 KiB
Plaintext
|
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
|
||
|
|
|
||
|
|
:link(lws,http://lammps.sandia.gov)
|
||
|
|
:link(ld,Manual.html)
|
||
|
|
:link(lc,Section_commands.html#comm)
|
||
|
|
|
||
|
|
:line
|
||
|
|
|
||
|
|
compute inertia/chunk command :h3
|
||
|
|
|
||
|
|
[Syntax:]
|
||
|
|
|
||
|
|
compute ID group-ID inertia/chunk chunkID :pre
|
||
|
|
|
||
|
|
ID, group-ID are documented in "compute"_compute.html command
|
||
|
|
inertia/molecule = style name of this compute command
|
||
|
|
chunkID = ID of "compute chunk/atom"_compute_chunk_atom.html command :ul
|
||
|
|
|
||
|
|
[Examples:]
|
||
|
|
|
||
|
|
compute 1 fluid inertia/chunk molchunk :pre
|
||
|
|
|
||
|
|
[Description:]
|
||
|
|
|
||
|
|
Define a computation that calculates the inertia tensor for multiple
|
||
|
|
chunks of atoms.
|
||
|
|
|
||
|
|
In LAMMPS, chunks are collections of atoms defined by a "compute
|
||
|
|
chunk/atom"_compute_chunk_atom.html command, which assigns each atom
|
||
|
|
to a single chunk (or no chunk). The ID for this command is specified
|
||
|
|
as chunkID. For example, a single chunk could be the atoms in a
|
||
|
|
molecule or atoms in a spatial bin. See the "compute
|
||
|
|
chunk/atom"_compute_chunk_atom.html doc page and ""Section_howto
|
||
|
|
23"_Section_howto.html#howto_23 for details of how chunks can be
|
||
|
|
defined and examples of how they can be used to measure properties of
|
||
|
|
a system.
|
||
|
|
|
||
|
|
This compute calculates the 6 components of the symmetric intertia
|
||
|
|
tensor for each chunk, ordered Ixx,Iyy,Izz,Ixy,Iyz,Ixz. The
|
||
|
|
calculation includes all effects due to atoms passing thru periodic
|
||
|
|
boundaries.
|
||
|
|
|
||
|
|
Note that only atoms in the specified group contribute to the
|
||
|
|
calculation. The "compute chunk/atom"_compute_chunk_atom.html command
|
||
|
|
defines its own group; atoms will have a chunk ID = 0 if they are not
|
||
|
|
in that group, signifying they are not assigned to a chunk, and will
|
||
|
|
thus also not contribute to this calculation. You can specify the
|
||
|
|
"all" group for this command if you simply want to include atoms with
|
||
|
|
non-zero chunk IDs.
|
||
|
|
|
||
|
|
IMPORTANT NOTE: The coordinates of an atom contribute to the chunk's
|
||
|
|
inertia tensor in "unwrapped" form, by using the image flags
|
||
|
|
associated with each atom. See the "dump custom"_dump.html command
|
||
|
|
for a discussion of "unwrapped" coordinates. See the Atoms section of
|
||
|
|
the "read_data"_read_data.html command for a discussion of image flags
|
||
|
|
and how they are set for each atom. You can reset the image flags
|
||
|
|
(e.g. to 0) before invoking this compute by using the "set
|
||
|
|
image"_set.html command.
|
||
|
|
|
||
|
|
The simplest way to output the results of the compute inertia/chunk
|
||
|
|
calculation to a file is to use the "fix ave/time"_fix_ave_time.html
|
||
|
|
command, for example:
|
||
|
|
|
||
|
|
compute cc1 chunk/atom molecule
|
||
|
|
compute myChunk all inertia/chunk cc1
|
||
|
|
fix 1 all ave/time 100 1 100 c_myChunk file tmp.out mode vector :pre
|
||
|
|
|
||
|
|
[Output info:]
|
||
|
|
|
||
|
|
This compute calculates a global array where the number of rows = the
|
||
|
|
number of chunks {Nchunk} as calculated by the specified "compute
|
||
|
|
chunk/atom"_compute_chunk_atom.html command. The number of columns =
|
||
|
|
6 for the 6 components of the inertia tensor for each chunk, ordered
|
||
|
|
as listed above. These values can be accessed by any command that
|
||
|
|
uses global array values from a compute as input. See "Section_howto
|
||
|
|
15"_Section_howto.html#howto_15 for an overview of LAMMPS output
|
||
|
|
options.
|
||
|
|
|
||
|
|
The array values are "intensive". The array values will be in
|
||
|
|
mass*distance^2 "units"_units.html.
|
||
|
|
|
||
|
|
[Restrictions:] none
|
||
|
|
|
||
|
|
[Related commands:]
|
||
|
|
|
||
|
|
"variable inertia() function"_variable.html
|
||
|
|
|
||
|
|
[Default:] none
|