Atomistic simulation and virtual diffraction characterization of homophase and heterophase alumina interfaces

The objective of this work is to elucidate the structure and energy of 12 homophase and heterophase alumina interfaces using atomistic simulations with the ReaxFF potential. First, the computational methods are validated by exploring a set of five α-Al2O3 symmetric tilt twin interfaces. The interface structures and energies for most homophase α-Al2O3 twins are in good agreement with prior atomistic studies; however, small deviations occur for select α-Al2O3 interfaces due to the larger, more appropriate interface areas explored in this work. Next, select experimentally observed κ-Al2O3, γ-Al2O3, and θ-Al2O3 homophase interfaces as well as heterophase α-Al2O3//γ-Al2O3 and θ-Al2O3//γ-Al2O3 interfaces are investigated for the first time using atomistic simulations to elucidate their atomic structure, including terminating plane(s) and relaxations, and to compute interface energies. ReaxFF predicts that the γ-Al2O3 {1 1 1} twin and the θ-Al2O3 {2 0 0} twin interfaces have energies of the same order as the lowest-energy α-Al2O3 prismatic twin boundary and that the heterophase α-Al2O3 (0 0 0 1)//γ-Al2O3 (1 1 1) interface has the lowest energy of all interfaces studied. Lastly, virtual selected-area electron diffraction patterns of select interfaces are used to experimentally validate the predicted interface structures. Because a consistent computational method is implemented throughout this work, the computed interface energies can be incorporated in future predictive mesoscale simulations of polymorphic alumina.