1.. index:: angle_style cosine/delta
2.. index:: angle_style cosine/delta/omp
3
4angle_style cosine/delta command
5================================
6
7Accelerator Variants: *cosine/delta/omp*
8
9Syntax
10""""""
11
12.. code-block:: LAMMPS
13
14   angle_style cosine/delta
15
16Examples
17""""""""
18
19.. code-block:: LAMMPS
20
21   angle_style cosine/delta
22   angle_coeff 2*4 75.0 100.0
23
24Description
25"""""""""""
26
27The *cosine/delta* angle style uses the potential
28
29.. math::
30
31   E = K [1 - \cos(\theta - \theta_0)]
32
33where :math:`\theta_0` is the equilibrium value of the angle, and :math:`K` is a
34prefactor.  Note that the usual 1/2 factor is included in :math:`K`.
35
36The following coefficients must be defined for each angle type via the
37:doc:`angle_coeff <angle_coeff>` command as in the example above, or in
38the data file or restart files read by the :doc:`read_data <read_data>`
39or :doc:`read_restart <read_restart>` commands:
40
41* :math:`K` (energy)
42* :math:`\theta_0` (degrees)
43
44:math:`\theta_0` is specified in degrees, but LAMMPS converts it to radians
45internally.
46
47----------
48
49.. include:: accel_styles.rst
50
51----------
52
53Restrictions
54""""""""""""
55
56This angle style can only be used if LAMMPS was built with the
57EXTRA-MOLECULE package.  See the :doc:`Build package <Build_package>` doc page
58for more info.
59
60Related commands
61""""""""""""""""
62
63:doc:`angle_coeff <angle_coeff>`, :doc:`angle_style cosine/squared <angle_cosine_squared>`
64
65Default
66"""""""
67
68none
69