derived class of sw

doc/src/pair_sw_mod.rst

@@ -0,0 +1,103 @@
+.. index:: pair_style sw/mod
+
+pair_style sw/mod command
+=====================
+
+Syntax
+""""""
+
+.. code-block:: LAMMPS
+
+   pair_style sw/mod
+
+Examples
+""""""""
+
+.. code-block:: LAMMPS
+
+   pair_style sw/mod
+   pair_coeff * * tmd.sw.mod Mo S S
+
+Description
+"""""""""""
+
+The *sw/mod* style computes the energy E of a system of atoms, whose
+formula is the same as the Stillinger-Weber potential :doc:`pair_style sw <pair_sw>`.
+The only modification is in the three-body term, where 
+:math:`\delta = \cos \theta_{ijk} - \cos \theta_{0ijk}`
+is modified with the following function:
+
+.. math::
+
+  g_C(\delta) & = \left\{ \begin{array} {r@{\quad:\quad}l}
+    1 & \delta < \delta_1 \\
+    \frac{1}{2} + \frac{1}{2} \cos \left( \pi \frac{\delta-\delta_1}{\delta_2 - \delta_1} \right) &
+      \delta_1 < \delta < \delta_2 \\
+    0 & \delta > \delta_2
+    \end{array} \right. \\
+
+
+This potential is designed for simulations of materials when
+distinguishing three-body angles are necessary, such as borophene
+and transition metal dichalcogenide, which cannot be described 
+by the original code for the Stillinger-Weber potential. Validation, 
+benchmark tests, and applications of the *modify* keyword can be found in
+:ref:`(Jiang_1) <Jiang1>` and :ref:`(Jiang_2) <Jiang2>`.
+
+----------
+
+Mixing, shift, table, tail correction, restart, rRESPA info
+"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
+
+For atom type pairs I,J and I != J, where types I and J correspond to
+two different element types, mixing is performed by LAMMPS as
+described above from values in the potential file.
+
+This pair style does not support the :doc:`pair_modify <pair_modify>`
+shift, table, and tail options.
+
+This pair style does not write its information to :doc:`binary restart files <restart>`, since it is stored in potential files.  Thus, you
+need to re-specify the pair_style and pair_coeff commands in an input
+script that reads a restart file.
+
+This pair style can only be used via the *pair* keyword of the
+:doc:`run_style respa <run_style>` command.  It does not support the
+*inner*, *middle*, *outer* keywords.
+
+----------
+
+Restrictions
+""""""""""""
+
+This pair style is part of the MANYBODY package.  It is only enabled
+if LAMMPS was built with that package.  See the :doc:`Build package <Build_package>` page for more info.
+
+This pair style requires the :doc:`newton <newton>` setting to be "on"
+for pair interactions.
+
+The Stillinger-Weber potential files provided with LAMMPS (see the
+potentials directory) are parameterized for metal :doc:`units <units>`.
+You can use the SW potential with any LAMMPS units, but you would need
+to create your own SW potential file with coefficients listed in the
+appropriate units if your simulation does not use "metal" units.
+
+Related commands
+""""""""""""""""
+:doc:`pair_coeff <pair_coeff>`
+
+:doc:`pair_style sw <pair_sw>`
+
+Default
+"""""""
+
+none
+
+----------
+
+.. _Jiang1:
+
+**(Jiang_1)** J.-W. Jiang, Nanotechnology 26, 315706 (2015).
+
+.. _Jiang2:
+
+**(Jiang_2)** J.-W. Jiang, Acta Mech. Solida. Sin 32, 17 (2019).