Unraveling the dynamics of stacking fault nucleation in ceramics: A case study of aluminum nitride

Stacking fault (SF), originating from the emission of partial dislocations, wields significant influence over the structural and physicochemical traits of ceramic materials. Yet, the intricate atomic dynamics driving SF nucleation remain obscured. Here, we introduce an improved methodology for computing the generalized stacking fault energy (GSFE) in ceramics, integrating uneven Degrees of Freedom (DOFs) for distinct lattice sites. This refinement has yielded substantial energy advantages over the traditional rigid shift method inherited from metallic systems. Our findings underscore that the relaxation of nonmetallic N atoms within the SF region is pivotal for achieving a more realistic SF simulation. This, in turn, unveils the involvement of N atom migration within the SF region between different aluminum tetrahedral sites during SF nucleation. By alleviating the energy barrier, this relaxation contrasts with previous simulations where nonmetallic elements remained more rigid. This work demonstrates the atomic dynamics of SF nucleation in ceramics and breaks the conventional wisdom of uniformly applying constraints for GSFE computations.