The development of methods for the accurate calculation of interfacial
free energies would have important consequences for predicting the me
chanical and thermodynamic behavior of metals and other materials. For
example, the passage of a dislocation through crystals is accompanied
by the formation of various extended defects, such as stacking faults
and antiphase boundaries, The associated formation energies influence
the mobility of the dislocation and distinguish between slip systems
and thus greatly affect the mechanical properties of metals and alloys
. Also, nucleation theory relates the rate of precipitate formation to
the interfacial free energy between the two phases, thus controlling
the thermodynamic stability of solid solutions, This article discusses
the general problem in calculating interfacial free energies in solid
s and describes a new method for antiphase boundaries and chemically d
isordered systems: simulated alchemy. Sample calculations for the APE
on the (111) face of Ni3Al are given using a Finnis-Sinclair-type pote
ntial.