forked from lijiext/lammps
102 lines
2.8 KiB
Plaintext
102 lines
2.8 KiB
Plaintext
.. index:: dihedral_style harmonic
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dihedral_style harmonic command
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===============================
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dihedral_style harmonic/intel command
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=====================================
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dihedral_style harmonic/omp command
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===================================
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Syntax
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""""""
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.. parsed-literal::
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dihedral_style harmonic
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Examples
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""""""""
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.. parsed-literal::
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dihedral_style harmonic
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dihedral_coeff 1 80.0 1 2
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Description
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"""""""""""
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The *harmonic* dihedral style uses the potential
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.. image:: Eqs/dihedral_harmonic.jpg
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:align: center
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The following coefficients must be defined for each dihedral type via the
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:doc:`dihedral_coeff <dihedral_coeff>` command as in the example above, or in
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the data file or restart files read by the :doc:`read_data <read_data>`
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or :doc:`read_restart <read_restart>` commands:
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* K (energy)
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* d (+1 or -1)
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* n (integer >= 0)
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.. note::
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Here are important points to take note of when defining LAMMPS
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dihedral coefficients for the harmonic style, so that they are
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compatible with how harmonic dihedrals are defined by other force
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fields:
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* The LAMMPS convention is that the trans position = 180 degrees, while
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in some force fields trans = 0 degrees.
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* Some force fields reverse the sign convention on *d*\ .
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* Some force fields let *n* be positive or negative which corresponds to
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*d* = 1 or -1 for the harmonic style.
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----------
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Styles with a *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in :doc:`Section_accelerate <Section_accelerate>`
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the :ref:`Making LAMMPS <start_3>` section for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
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use the :doc:`suffix <suffix>` command in your input script.
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See :doc:`Section_accelerate <Section_accelerate>` of the manual for
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more instructions on how to use the accelerated styles effectively.
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----------
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Restrictions
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""""""""""""
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This dihedral style can only be used if LAMMPS was built with the
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MOLECULE package (which it is by default). See the :ref:`Making LAMMPS <start_3>` section for more info on packages.
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Related commands
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""""""""""""""""
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:doc:`dihedral_coeff <dihedral_coeff>`
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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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