1.. index:: angle_style cosine/shift 2.. index:: angle_style cosine/shift/omp 3 4angle_style cosine/shift command 5================================ 6 7Accelerator Variants: *cosine/shift/omp* 8 9Syntax 10"""""" 11 12.. code-block:: LAMMPS 13 14 angle_style cosine/shift 15 16Examples 17"""""""" 18 19.. code-block:: LAMMPS 20 21 angle_style cosine/shift 22 angle_coeff * 10.0 45.0 23 24Description 25""""""""""" 26 27The *cosine/shift* angle style uses the potential 28 29.. math:: 30 31 E = -\frac{U_{\text{min}}}{2} \left[ 1 + \cos(\theta-\theta_0) \right] 32 33where :math:`\theta_0` is the equilibrium angle. The potential is bounded 34between :math:`-U_{\text{min}}` and zero. In the neighborhood of the minimum 35:math:`E = - U_{\text{min}} + U_{\text{min}}/4(\theta - \theta_0)^2` hence 36the spring constant is :math:`\frac{U_{\text{min}}}{2}`. 37 38The following coefficients must be defined for each angle type via the 39:doc:`angle_coeff <angle_coeff>` command as in the example above, or in 40the data file or restart files read by the :doc:`read_data <read_data>` 41or :doc:`read_restart <read_restart>` commands: 42 43* :math:`U_{\text{min}}` (energy) 44* :math:`\theta` (angle) 45 46---------- 47 48.. include:: accel_styles.rst 49 50---------- 51 52Restrictions 53"""""""""""" 54 55This angle style can only be used if LAMMPS was built with the 56EXTRA-MOLECULE package. See the :doc:`Build package <Build_package>` doc 57page for more info. 58 59Related commands 60"""""""""""""""" 61 62:doc:`angle_coeff <angle_coeff>`, 63:doc:`angle_style cosine/shift/exp <angle_cosine_shift_exp>` 64 65Default 66""""""" 67 68none 69