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edits to 1st paragraph of description

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Steve Plimpton
2022-06-10 08:30:23 -06:00
parent 495418158a
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1 changed files with 36 additions and 28 deletions
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doc/src/compute_ave_sphere_atom.rst
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@ -35,18 +35,24 @@ Examples
Description
"""""""""""
Define a computation that calculates the local mass density and temperature
for each atom and neighbors inside a spherical cutoff. The center-of-mass
velocity of the atoms in the sphere is subtracted out before computing the
temperature, which leaves only the thermal velocity, similar to :doc:`compute temp/com <compute_temp_com>`.
Define a computation that calculates the local mass density and
temperature for each atom based on its neighbors inside a spherical
cutoff. If an atom has M neighbors, then its local mass density is
calculated as the sum of its mass and its M neighbor masses, divided
by the volume of the cutoff sphere (or circle in 2d). The local
temperature of the atom is calculated as the temperature of the
collection of M+1 atoms, after subtracting the center-of-mass velocity
of the M+1 atoms from each of the M+1 atom's velocities. This is
effectively the thermal velocity of the neighborhood of the central
atom, similar to :doc:`compute temp/com <compute_temp_com>`.
The optional keyword *cutoff* defines the distance cutoff
used when searching for neighbors. The default value is the cutoff
specified by the pair style. If no pair style is defined, then a cutoff
must be defined using this keyword. If the specified cutoff is larger than
that of the pair_style plus neighbor skin (or no pair style is defined),
the *comm_modify cutoff* option must also be set to match that of the
*cutoff* keyword.
The optional keyword *cutoff* defines the distance cutoff used when
searching for neighbors. The default value is the cutoff specified by
the pair style. If no pair style is defined, then a cutoff must be
defined using this keyword. If the specified cutoff is larger than
that of the pair_style plus neighbor skin (or no pair style is
defined), the *comm_modify cutoff* option must also be set to match
that of the *cutoff* keyword.
The neighbor list needed to compute this quantity is constructed each
time the calculation is performed (i.e. each time a snapshot of atoms
@ -57,16 +63,16 @@ too frequently.
If you have a bonded system, then the settings of
:doc:`special_bonds <special_bonds>` command can remove pairwise
interactions between atoms in the same bond, angle, or dihedral. This
is the default setting for the :doc:`special_bonds <special_bonds>`
command, and means those pairwise interactions do not appear in the
neighbor list. Because this compute uses the neighbor list, it also means
those pairs will not be included in the order parameter. This
difficulty can be circumvented by writing a dump file, and using the
:doc:`rerun <rerun>` command to compute the order parameter for
snapshots in the dump file. The rerun script can use a
:doc:`special_bonds <special_bonds>` command that includes all pairs in
the neighbor list.
interactions between atoms in the same bond, angle, or dihedral.
This is the default setting for the :doc:`special_bonds
<special_bonds>` command, and means those pairwise interactions do
not appear in the neighbor list. Because this compute uses the
neighbor list, it also means those pairs will not be included in
the order parameter. This difficulty can be circumvented by
writing a dump file, and using the :doc:`rerun <rerun>` command to
compute the order parameter for snapshots in the dump file. The
rerun script can use a :doc:`special_bonds <special_bonds>` command
that includes all pairs in the neighbor list.
----------
@ -79,18 +85,20 @@ too frequently.
Output info
"""""""""""
This compute calculates a per-atom array with two columns: mass density in density
:doc:`units <units>` and temperature in temperature :doc:`units <units>`.
This compute calculates a per-atom array with two columns: mass
density in density :doc:`units <units>` and temperature in temperature
:doc:`units <units>`.
These values can be accessed by any command that uses per-atom values
from a compute as input. See the :doc:`Howto output <Howto_output>` doc
page for an overview of LAMMPS output options.
from a compute as input. See the :doc:`Howto output <Howto_output>`
doc page for an overview of LAMMPS output options.
Restrictions
""""""""""""
This compute is part of the EXTRA-COMPUTE package. It is only enabled if
LAMMPS was built with that package. See the :doc:`Build package <Build_package>` page for more info.
This compute is part of the EXTRA-COMPUTE package. It is only enabled
if LAMMPS was built with that package. See the :doc:`Build package
<Build_package>` page for more info.
Related commands
""""""""""""""""
@ -100,5 +108,5 @@ Related commands
Default
"""""""
The option defaults are *cutoff* = pair style cutoff
The option defaults are *cutoff* = pair style cutoff.