  A semi-empirical formalism based on the second moment tight binding approach,
considering two bands is presented for deriving interatomic potentials for
magnetic d-band materials and transition metal alloys. It incorporates an
empirical local exchange interaction, which accounts for magnetic effects
without increasing the computing time required for force evaluation. The
consequences of applying a two-band picture to transition metal alloys and
transition metal impurities is examined, which combined with evidence from {\it
ab initio calculations} leads to some surprisingly simplifying conclusions.
