Minor doc changes & rename store_contacts to contacts

.. parsed-literal::

   fix ID group-ID wall/gran fstyle fstyle_params wallstyle args keyword values ... [store_contacts]

   fix ID group-ID wall/gran fstyle fstyle_params wallstyle args keyword values ...

* ID, group-ID are documented in :doc:`fix <fix>` command

* wall/gran = style name of this fix command

         radius = cylinder radius (distance units)

* zero or more keyword/value pairs may be appended to args

* keyword = *wiggle* or *shear* or *store_contacts*

* keyword = *wiggle* or *shear* or *contacts*

  .. parsed-literal::

       *shear* values = dim vshear

         dim = *x* or *y* or *z*

         vshear = magnitude of shear velocity (velocity units)

      *store_contacts* = store contact information for each particle colliding with wall

      *contacts* value = none

         store contact information for each particle colliding with wall

Examples

   fix 3 all wall/gran/region granular hooke 1000.0 50.0 tangential linear_nohistory 1.0 0.4 damping velocity region myBox

   fix 4 all wall/gran/region granular jkr 1e5 1500.0 0.3 10.0 tangential mindlin NULL 1.0 0.5 rolling sds 500.0 200.0 0.5 twisting marshall region myCone

   fix 5 all wall/gran/region granular dmt 1e5 0.2 0.3 10.0 tangential mindlin NULL 1.0 0.5 rolling sds 500.0 200.0 0.5 twisting marshall damping tsuji region myCone

   fix 6 all wall/gran hooke  200000.0 NULL 50.0 NULL 0.5 0 xplane -10.0 10.0 store_contacts

   fix 6 all wall/gran hooke  200000.0 NULL 50.0 NULL 0.5 0 xplane -10.0 10.0 contacts

Description

"""""""""""

restart file, so that the operation of the fix continues in an

uninterrupted fashion.

If the :code:`store_contacts` option is used, this fix will store the contact

information for each atom that interacts with the wall. The following table

summarizes which values are available as per-atom quantities

(:code:`f_FIXID[Index]`) to access by various :doc:`output commands <Howto_output>`:

+-------+----------------------------------------------------+

| Index | Value                                              |

+=======+====================================================+

|     1 | Atom ID                                            |

+-------+----------------------------------------------------+

|     2 | Force :math:`f_x` exerted on the wall              |

+-------+----------------------------------------------------+

|     3 | Force :math:`f_y` exerted on the wall              |

+-------+----------------------------------------------------+

|     4 | Force :math:`f_z` exerted on the wall              |

+-------+----------------------------------------------------+

|     5 | :math:`\Delta x` between wall surface and particle |

+-------+----------------------------------------------------+

|     6 | :math:`\Delta y` between wall surface and particle |

+-------+----------------------------------------------------+

|     7 | :math:`\Delta z` between wall surface and particle |

+-------+----------------------------------------------------+

|     8 | Radius :math:`r` of atom                           |

+-------+----------------------------------------------------+

If the :code:`contacts` option is used, this fix will store the contact

information for each atom that interacts with the wall as per-atom array with 8

columns. The values of these columns are listed in the following table:

+-------+----------------------------------------------------+----------------+

| Index | Value                                              | Units          |

+=======+====================================================+================+

|     1 | Atom ID                                            |                |

+-------+----------------------------------------------------+----------------+

|     2 | Force :math:`f_x` exerted on the wall              | force units    |

+-------+----------------------------------------------------+----------------+

|     3 | Force :math:`f_y` exerted on the wall              | force units    |

+-------+----------------------------------------------------+----------------+

|     4 | Force :math:`f_z` exerted on the wall              | force units    |

+-------+----------------------------------------------------+----------------+

|     5 | :math:`\Delta x` between wall surface and particle | distance units |

+-------+----------------------------------------------------+----------------+

|     6 | :math:`\Delta y` between wall surface and particle | distance units |

+-------+----------------------------------------------------+----------------+

|     7 | :math:`\Delta z` between wall surface and particle | distance units |

+-------+----------------------------------------------------+----------------+

|     8 | Radius :math:`r` of atom                           | distance units |

+-------+----------------------------------------------------+----------------+

None of the :doc:`fix_modify <fix_modify>` options are relevant to this fix.

No parameter of this fix can be used with the *start/stop* keywords of the

      vshear = force->numeric(FLERR,arg[iarg+2]);

      wshear = 1;

      iarg += 3;

    } else if (strcmp(arg[iarg],"store_contacts") == 0) {

    } else if (strcmp(arg[iarg],"contacts") == 0) {

      peratom_flag = 1;

      size_peratom_cols = 8;

      peratom_freq = 1;