Migration of Aluminum Atoms in the Transformation of γ- to θ-Alumina

摘要

γ- and θ-alumina are two metastable phases of aluminum oxide observed along the thermal dehydration sequence of boehmite before conversion to the final product α-alumina. The transformation from γ- to θ-alumina was studied by using Al_(16),O_(24) cells. Motion of some Al atoms from their γ-alumina positions to new positions and no O motions result in an approximate structure that, upon relaxation by first-principles calculations, becomes the known θ-alumina structure. Total-energy calculations along the paths of the atomic motions have been used to map out transformation pathways. The model accurately predicts experimentally observed domain boundaries in θ-alumina and the γ- to θ-alumina conversion rate.