FREE-ENERGY CALCULATION OF EXTENDED DEFECTS THROUGH SIMULATED ALCHEMY- APPLICATION TO NI3AL ANTIPHASE BOUNDARIES

Accurate calculation of the free energy of defects is important in und erstanding many mechanical processes and properties in materials. Here a method is proposed for directly calculating the free energy differe nce between bulk crystal and defect multi-component atomic systems. Ba sed on lambda-integration techniques it involves defining a nonphysica l but reversible thermodynamic pathway that connects the bulk referenc e crystal and defect structures. This pathway can be thought of as an alchemic route to the free energy as selected atoms are allowed to tra nsform their atomic character. The method is demonstrated by using it to calculate the free energy of Ni3Al antiphase boundaries where atomi c interactions are modeled through a Finnis-Sinclair type potential.