Atomistic Simulations of the Crystalline-to-Amorphous Transformation of γ-AlO Nanoparticles: Delicate Interplay between Lattice Distortions, Stresses, and Space Charges.

The size-dependent phase stability of γ-AlO was studied by large-scale molecular dynamics simulations over a wide temperature range from 300 to 900 K. For the γ-AlO crystal, a bulk transformation to α-AlO by an FCC-to-HCP transition of the O sublattice is still kinetically hindered at 900 K. However, local distortions of the FCC O-sublattice by the formation of quasi-octahedral Al local coordination spheres become thermally activated, as driven by the partial covalency of the Al-O bond.