addressed incompatibility with long range coulombics

Specifically 1-2 interactions must have weights of zero, 1-3

interactions must either have weights of unity or :doc:`special_bonds

angle yes <special_bonds>` must be used, and 1-4 interactions must

have weights of unity or the *dihedral* setting must be turned on or

:doc:`special_bonds dihedral yes <special_bonds>` must be used.

have weights of unity or :doc:`special_bonds dihedral yes <special_bonds>` 

must be used.

If this command is used to create bonded interactions between

particles that are further apart than usual (e.g. 1-5 or 1-6

This bond style requires use of a :doc:`pair_style <pair_style>` which

computes a pairwise interaction.  Many-body potentials do not.

Q: Does this command work with long-range Coulombics?  E.g. if used to

weight 1-5 interactions between charged particles and also used with

PPPM, does it give the right answer?  The special bond weight settings

are treated explicity in pair styles like pair lj/cut/coul/long.

Either way, the answer to this Q should be explained on this page.

And if the answer is no, then I think an error check should be made in

the code.

This command is not compatible with long-range Coulombic interactions. If a 

`kspace_style <kspace_style>` is declared, an error will be issued.

Related commands

""""""""""""""""

                                       force->special_coul[3] != 1.0))

    error->all(FLERR,"Invalid 1-4 setting for bond style special.");

  if (force->kspace != NULL)

    error->all(FLERR,"Bond style special is not compatible with long range "

        "Coulombic interactions");

}

/* ---------------------------------------------------------------------- */

Bond style special must be used with 1.0 factors for 1-4 special bonds or the

dihedral keyword set to yes.

E: Bond style special is not compatible with long range Coulombic interactions.

Self-explanatory.

*/