A COMPUTATION OF (110) INTRINSIC STACKING-FAULT ENERGIES IN B2 ORDERED ALLOYS

The energies E(f) of fully relaxed 'generalized' intrinsic stacking faults on (110) planes, with fault vectors f running over the total unit cell of these planes, are computed for a B2 ordered (CsCl structure) alloy, using three sets of pair potentials. With the first set, compound of Johnson type potentials, a surface E(f) very similar to that of pure b. c. c. metals is obtained, with no other local minima than the perfect lattice and the antiphase boundary. Analyzing the origin of the local minima at f//1 and f//2, it is possible to derive a second set of pair potentials for Fe-Al which does not show these minima.