forked from lijiext/lammps
123 lines
4.0 KiB
Plaintext
123 lines
4.0 KiB
Plaintext
.. index:: bond_style
|
|
|
|
bond_style command
|
|
==================
|
|
|
|
Syntax
|
|
""""""
|
|
|
|
.. parsed-literal::
|
|
|
|
bond_style style args
|
|
|
|
* style = *none* or *hybrid* or *class2* or *fene* or *fene/expand* or *harmonic* or *morse* or *nonlinear* or *quartic*
|
|
|
|
.. parsed-literal::
|
|
|
|
args = none for any style except *hybrid*
|
|
*hybrid* args = list of one or more styles
|
|
|
|
Examples
|
|
""""""""
|
|
|
|
.. parsed-literal::
|
|
|
|
bond_style harmonic
|
|
bond_style fene
|
|
bond_style hybrid harmonic fene
|
|
|
|
Description
|
|
"""""""""""
|
|
|
|
Set the formula(s) LAMMPS uses to compute bond interactions between
|
|
pairs of atoms. In LAMMPS, a bond differs from a pairwise
|
|
interaction, which are set via the :doc:`pair_style <pair_style>`
|
|
command. Bonds are defined between specified pairs of atoms and
|
|
remain in force for the duration of the simulation (unless the bond
|
|
breaks which is possible in some bond potentials). The list of bonded
|
|
atoms is read in by a :doc:`read_data <read_data>` or
|
|
:doc:`read_restart <read_restart>` command from a data or restart file.
|
|
By contrast, pair potentials are typically defined between all pairs
|
|
of atoms within a cutoff distance and the set of active interactions
|
|
changes over time.
|
|
|
|
Hybrid models where bonds are computed using different bond potentials
|
|
can be setup using the *hybrid* bond style.
|
|
|
|
The coefficients associated with a bond style can be specified in a
|
|
data or restart file or via the :doc:`bond_coeff <bond_coeff>` command.
|
|
|
|
All bond potentials store their coefficient data in binary restart
|
|
files which means bond_style and :doc:`bond_coeff <bond_coeff>` commands
|
|
do not need to be re-specified in an input script that restarts a
|
|
simulation. See the :doc:`read_restart <read_restart>` command for
|
|
details on how to do this. The one exception is that bond_style
|
|
*hybrid* only stores the list of sub-styles in the restart file; bond
|
|
coefficients need to be re-specified.
|
|
|
|
.. note::
|
|
|
|
When both a bond and pair style is defined, the
|
|
:doc:`special_bonds <special_bonds>` command often needs to be used to
|
|
turn off (or weight) the pairwise interaction that would otherwise
|
|
exist between 2 bonded atoms.
|
|
|
|
In the formulas listed for each bond style, *r* is the distance
|
|
between the 2 atoms in the bond.
|
|
|
|
|
|
----------
|
|
|
|
|
|
Here is an alphabetic list of bond styles defined in LAMMPS. Click on
|
|
the style to display the formula it computes and coefficients
|
|
specified by the associated :doc:`bond_coeff <bond_coeff>` command.
|
|
|
|
Note that there are also additional bond styles submitted by users
|
|
which are included in the LAMMPS distribution. The list of these with
|
|
links to the individual styles are given in the bond section of :ref:`this page <cmd_5>`.
|
|
|
|
* :doc:`bond_style none <bond_none>` - turn off bonded interactions
|
|
* :doc:`bond_style zero <bond_zero>` - topology but no interactions
|
|
* :doc:`bond_style hybrid <bond_hybrid>` - define multiple styles of bond interactions
|
|
|
|
* :doc:`bond_style class2 <bond_class2>` - COMPASS (class 2) bond
|
|
* :doc:`bond_style fene <bond_fene>` - FENE (finite-extensible non-linear elastic) bond
|
|
* :doc:`bond_style fene/expand <bond_fene_expand>` - FENE bonds with variable size particles
|
|
* :doc:`bond_style harmonic <bond_harmonic>` - harmonic bond
|
|
* :doc:`bond_style morse <bond_morse>` - Morse bond
|
|
* :doc:`bond_style nonlinear <bond_nonlinear>` - nonlinear bond
|
|
* :doc:`bond_style quartic <bond_quartic>` - breakable quartic bond
|
|
* :doc:`bond_style table <bond_table>` - tabulated by bond length
|
|
|
|
|
|
----------
|
|
|
|
|
|
Restrictions
|
|
""""""""""""
|
|
|
|
|
|
Bond styles can only be set for atom styles that allow bonds to be
|
|
defined.
|
|
|
|
Most bond styles are part of the MOLECULE package. They are only
|
|
enabled if LAMMPS was built with that package. See the :ref:`Making LAMMPS <start_3>` section for more info on packages.
|
|
The doc pages for individual bond potentials tell if it is part of a
|
|
package.
|
|
|
|
Related commands
|
|
""""""""""""""""
|
|
|
|
:doc:`bond_coeff <bond_coeff>`, :doc:`delete_bonds <delete_bonds>`
|
|
|
|
Default
|
|
"""""""
|
|
|
|
bond_style none
|
|
|
|
|
|
.. _lws: http://lammps.sandia.gov
|
|
.. _ld: Manual.html
|
|
.. _lc: Section_commands.html#comm
|