(2) outer cutoff (distance units)
         ewald
               (1) cutoff distance for near-field portion (distance units)
               (2) accuracy criterion
         pppm
               (1) cutoff distance for near-field portion (distance units)
               (2) accuracy criterion
         charmm/switch
               (1) inner cutoff (distance units)
               (2) outer cutoff (distance units)
         debye
               (1) cutoff distance (distance units)
               (2) kappa (inverse d