forked from lijiext/lammps
117 lines
3.7 KiB
Plaintext
117 lines
3.7 KiB
Plaintext
.. index:: angle_coeff
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angle_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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angle_coeff N args
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* N = angle type (see asterisk form below)
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* args = coefficients for one or more angle types
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Examples
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""""""""
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.. parsed-literal::
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angle_coeff 1 300.0 107.0
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angle_coeff * 5.0
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angle_coeff 2*10 5.0
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Description
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"""""""""""
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Specify the angle force field coefficients for one or more angle types.
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The number and meaning of the coefficients depends on the angle style.
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Angle 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 angle types. This takes the
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form "*" or "*n" or "n*" or "m*n". If N = the number of angle 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 an angle_coeff command can override a previous setting
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for the same angle type. For example, these commands set the coeffs
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for all angle types, then overwrite the coeffs for just angle type 2:
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.. parsed-literal::
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angle_coeff * 200.0 107.0 1.2
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angle_coeff 2 50.0 107.0
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A line in a data file that specifies angle coefficients uses the exact
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same format as the arguments of the angle_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 "Angle 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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1 300.0 107.0
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The :doc:`angle_style class2 <angle_class2>` is an exception to this
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rule, in that an additional argument is used in the input script to
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allow specification of the cross-term coefficients. See its
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doc page for details.
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----------
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Here is an alphabetic list of angle 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:`angle_coeff <angle_coeff>` command.
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Note that there are also additional angle 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 angle section of :ref:`this page <cmd_5>`.
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* :doc:`angle_style none <angle_none>` - turn off angle interactions
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* :doc:`angle_style hybrid <angle_hybrid>` - define multiple styles of angle interactions
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* :doc:`angle_style charmm <angle_charmm>` - CHARMM angle
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* :doc:`angle_style class2 <angle_class2>` - COMPASS (class 2) angle
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* :doc:`angle_style cosine <angle_cosine>` - cosine angle potential
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* :doc:`angle_style cosine/delta <angle_cosine_delta>` - difference of cosines angle potential
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* :doc:`angle_style cosine/periodic <angle_cosine_periodic>` - DREIDING angle
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* :doc:`angle_style cosine/squared <angle_cosine_squared>` - cosine squared angle potential
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* :doc:`angle_style harmonic <angle_harmonic>` - harmonic angle
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* :doc:`angle_style table <angle_table>` - tabulated by angle
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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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An angle style must be defined before any angle coefficients are
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set, 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:`angle_style <angle_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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