git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@14950 f3b2605a-c512-4ea7-a41b-209d697bcdaa

doc/html/_sources/dihedral_harmonic.txt

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+.. index:: dihedral_style harmonic
+
+dihedral_style harmonic command
+===============================
+
+dihedral_style harmonic/intel command
+=====================================
+
+dihedral_style harmonic/omp command
+===================================
+
+Syntax
+""""""
+
+.. parsed-literal::
+
+   dihedral_style harmonic
+
+Examples
+""""""""
+
+.. parsed-literal::
+
+   dihedral_style harmonic
+   dihedral_coeff 1 80.0 1 2
+
+Description
+"""""""""""
+
+The *harmonic* dihedral style uses the potential
+
+.. image:: Eqs/dihedral_harmonic.jpg
+   :align: center
+
+The following coefficients must be defined for each dihedral type via the
+:doc:`dihedral_coeff <dihedral_coeff>` command as in the example above, or in
+the data file or restart files read by the :doc:`read_data <read_data>`
+or :doc:`read_restart <read_restart>` commands:
+
+* K (energy)
+* d (+1 or -1)
+* n (integer >= 0)
+
+.. note::
+
+   Here are important points to take note of when defining LAMMPS
+   dihedral coefficients for the harmonic style, so that they are
+   compatible with how harmonic dihedrals are defined by other force
+   fields:
+
+* The LAMMPS convention is that the trans position = 180 degrees, while
+  in some force fields trans = 0 degrees.
+* Some force fields reverse the sign convention on *d*\ .
+* Some force fields let *n* be positive or negative which corresponds to
+  *d* = 1 or -1 for the harmonic style.
+
+----------
+
+
+Styles with a *cuda*\ , *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
+functionally the same as the corresponding style without the suffix.
+They have been optimized to run faster, depending on your available
+hardware, as discussed in :doc:`Section_accelerate <Section_accelerate>`
+of the manual.  The accelerated styles take the same arguments and
+should produce the same results, except for round-off and precision
+issues.
+
+These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
+KOKKOS, USER-OMP and OPT packages, respectively.  They are only
+enabled if LAMMPS was built with those packages.  See the :ref:`Making LAMMPS <start_3>` section for more info.
+
+You can specify the accelerated styles explicitly in your input script
+by including their suffix, or you can use the :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
+use the :doc:`suffix <suffix>` command in your input script.
+
+See :doc:`Section_accelerate <Section_accelerate>` of the manual for
+more instructions on how to use the accelerated styles effectively.
+
+
+----------
+
+
+Restrictions
+""""""""""""
+
+
+This dihedral style can only be used if LAMMPS was built with the
+MOLECULE package (which it is by default).  See the :ref:`Making LAMMPS <start_3>` section for more info on packages.
+
+Related commands
+""""""""""""""""
+
+:doc:`dihedral_coeff <dihedral_coeff>`
+
+**Default:** none
+
+
+.. _lws: http://lammps.sandia.gov
+.. _ld: Manual.html
+.. _lc: Section_commands.html#comm