forked from lijiext/lammps
113 lines
3.5 KiB
Plaintext
113 lines
3.5 KiB
Plaintext
.. index:: bond_coeff
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bond_coeff command
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==================
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Syntax
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""""""
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.. parsed-literal::
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bond_coeff N args
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* N = bond type (see asterisk form below)
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* args = coefficients for one or more bond types
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Examples
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""""""""
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.. parsed-literal::
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bond_coeff 5 80.0 1.2
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bond_coeff * 30.0 1.5 1.0 1.0
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bond_coeff 1*4 30.0 1.5 1.0 1.0
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bond_coeff 1 harmonic 200.0 1.0
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Description
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"""""""""""
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Specify the bond force field coefficients for one or more bond types.
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The number and meaning of the coefficients depends on the bond style.
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Bond coefficients can also be set in the data file read by the
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:doc:`read_data <read_data>` command or in a restart file.
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N can be specified in one of two ways. An explicit numeric value can
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be used, as in the 1st example above. Or a wild-card asterisk can be
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used to set the coefficients for multiple bond types. This takes the
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form "*" or "*n" or "n*" or "m*n". If N = the number of bond types,
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then an asterisk with no numeric values means all types from 1 to N. A
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leading asterisk means all types from 1 to n (inclusive). A trailing
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asterisk means all types from n to N (inclusive). A middle asterisk
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means all types from m to n (inclusive).
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Note that using a bond_coeff command can override a previous setting
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for the same bond type. For example, these commands set the coeffs
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for all bond types, then overwrite the coeffs for just bond type 2:
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.. parsed-literal::
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bond_coeff * 100.0 1.2
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bond_coeff 2 200.0 1.2
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A line in a data file that specifies bond coefficients uses the exact
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same format as the arguments of the bond_coeff command in an input
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script, except that wild-card asterisks should not be used since
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coefficients for all N types must be listed in the file. For example,
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under the "Bond Coeffs" section of a data file, the line that
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corresponds to the 1st example above would be listed as
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.. parsed-literal::
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5 80.0 1.2
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----------
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Here is an alphabetic list of bond styles defined in LAMMPS. Click on
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the style to display the formula it computes and coefficients
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specified by the associated :doc:`bond_coeff <bond_coeff>` command.
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Note that here are also additional bond styles submitted by users
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which are included in the LAMMPS distribution. The list of these with
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links to the individual styles are given in the bond section of :ref:`this page <cmd_5>`.
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* :doc:`bond_style none <bond_none>` - turn off bonded interactions
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* :doc:`bond_style hybrid <bond_hybrid>` - define multiple styles of bond interactions
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* :doc:`bond_style class2 <bond_class2>` - COMPASS (class 2) bond
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* :doc:`bond_style fene <bond_fene>` - FENE (finite-extensible non-linear elastic) bond
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* :doc:`bond_style fene/expand <bond_fene_expand>` - FENE bonds with variable size particles
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* :doc:`bond_style harmonic <bond_harmonic>` - harmonic bond
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* :doc:`bond_style morse <bond_morse>` - Morse bond
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* :doc:`bond_style nonlinear <bond_nonlinear>` - nonlinear bond
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* :doc:`bond_style quartic <bond_quartic>` - breakable quartic bond
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* :doc:`bond_style table <bond_table>` - tabulated by bond length
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----------
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Restrictions
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""""""""""""
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This command must come after the simulation box is defined by a
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:doc:`read_data <read_data>`, :doc:`read_restart <read_restart>`, or
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:doc:`create_box <create_box>` command.
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A bond style must be defined before any bond coefficients are set,
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either in the input script or in a data file.
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Related commands
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""""""""""""""""
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:doc:`bond_style <bond_style>`
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**Default:** none
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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