short documentation file for the angle gaussian

doc/src/angle_gaussian.rst

@@ -0,0 +1,69 @@
+.. index:: angle_style gaussian
+
+angle_style gaussian command
+================================
+
+Syntax
+""""""
+
+.. code-block:: LAMMPS
+
+   angle_style gaussian
+
+Examples
+""""""""
+
+.. code-block:: LAMMPS
+
+   angle_style gaussian
+   angle_coeff 1 300.0 2 0.0128 0.375 80.0 0.0730 0.148 123.0
+
+Description
+"""""""""""
+
+The *gaussian* angle style uses the potential:
+
+.. math::
+
+   E = -k_B T ln\left(\sum_{i=1}^{n} \frac{A_i}{w_i \sqrt{\pi/2}} exp\left( \frac{-(\theta-\theta_{i})^2}{w_i^2})\right) \right)
+
+This analytical form is a suitable potential for obtaining
+mesoscale effective force fields which can reproduce target atomistic distributions :ref:`(Milano) <Milano0>`
+The following coefficients must be defined for each angle type via the
+:doc:`angle_coeff <angle_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:
+
+* T temperature at which the potential was derived
+* :math:`n` (integer >=1)
+* :math:`A_1` (-)
+* :math:`w_1` (-)
+* :math:`\theta_1` (degrees)
+* ...
+* :math:`A_n` (-)
+* :math:`w_n` (-)
+* :math:`\theta_n` (degrees)
+
+
+Restrictions
+""""""""""""
+
+This angle style can only be used if LAMMPS was built with the
+USER-MISC package.  See the :doc:`Build package <Build_package>` doc
+page for more info.
+
+Related commands
+""""""""""""""""
+
+:doc:`angle_coeff <angle_coeff>`
+
+Default
+"""""""
+
+none
+
+----------
+
+.. _Milano0:
+
+**(Milano)** G. Milano, S. Goudeau, F. Müller-Plathe, J. Polym. Sci. B Polym. Phys. 43, 871 (2005).