Keyword TOSI specifies a Born-Mayer potential of the form
The sum runs over all ions. Tosi-Fumi[#!tosif64!#] parameters in atomic units should be
entered after the Tosi keyword in the order , , , .
The ions are specified in file coords using PL and MI for plus and minus, respectively,
and can be in any order. There need not be equal numbers of positive and negative ions.
Note that the Welch potential has been fitted to include ion polarizabilities and is described below.