.. index:: angle_style cosine/periodic angle_style cosine/periodic command =================================== angle_style cosine/periodic/omp command ======================================= Syntax """""" .. parsed-literal:: angle_style cosine/periodic Examples """""""" .. parsed-literal:: angle_style cosine/periodic angle_coeff * 75.0 1 6 Description """"""""""" The *cosine/periodic* angle style uses the following potential, which is commonly used in the :ref:`DREIDING ` force field, particularly for organometallic systems where *n* = 4 might be used for an octahedral complex and *n* = 3 might be used for a trigonal center: .. image:: Eqs/angle_cosine_periodic.jpg :align: center where C, B and n are coefficients defined for each angle type. See :ref:`(Mayo) ` for a description of the DREIDING force field The following coefficients must be defined for each angle type via the :doc:`angle_coeff ` command as in the example above, or in the data file or restart files read by the :doc:`read_data ` or :doc:`read_restart ` commands: * C (energy) * B = 1 or -1 * n = 1, 2, 3, 4, 5 or 6 for periodicity Note that the prefactor C is specified and not the overall force constant K = C / n^2. When B = 1, it leads to a minimum for the linear geometry. When B = -1, it leads to a maximum for the linear geometry. ---------- 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 ` 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 ` 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 ` when you invoke LAMMPS, or you can use the :doc:`suffix ` command in your input script. See :doc:`Section_accelerate ` of the manual for more instructions on how to use the accelerated styles effectively. ---------- Restrictions """""""""""" This angle style can only be used if LAMMPS was built with the MOLECULE package (which it is by default). See the :ref:`Making LAMMPS ` section for more info on packages. Related commands """""""""""""""" :doc:`angle_coeff ` **Default:** none ---------- .. _cosine-Mayo: **(Mayo)** Mayo, Olfason, Goddard III, J Phys Chem, 94, 8897-8909 (1990). .. _lws: http://lammps.sandia.gov .. _ld: Manual.html .. _lc: Section_commands.html#comm