Generalized mechanism for the solid phase transition of M2O3 (M=AI, Ga) featuring single cation migration and martensitic lattice transformation

Al2O3 and Ga2O3 exhibit numerous crystal phases with distinct stabilities and material properties. However, the phase transitions among those materials are typically undesirable in industrial applications, making it imperative to elucidate the transition mechanisms between these phases. The configurational similarities between Al2O3 and Ga2O3 allow for the replication of phase transition pathways between these materials. In this study, we investigate the potential phase transition pathway of alumina from the θ-phase to the α-phase using stochastic surface walking global optimization based on global neural network potentials, while extending an existing Ga2O3 phase transition path. Through this exploration, we identify a novel single-atom migration pseudomartensitic mechanism, which combines martensitic transformation with single-atom diffusion. This discovery offers valuable insights for experimental endeavors aimed at stabilizing alumina in transitional phases.