Abstract:
Aluminum silicate based mineral “Sillimanite” (Al2SiO5) is important in the industrial
preparation of aluminum-silicon alloys and cement. In the present study classical pair potential
simulations are used to examine the intrinsic defect processes, diffusion pathways of Al3+ and O2−
ions together with their activation energies and promising dopants on the Al and Si sites in Al2SiO5.
The cation anti-site (Al-Si) defect cluster is calculated to be the most favorable defect, highlighting the
cation disorder in this material, in agreement with the experiment. The cation disorder is important
as this defect can change the mechanical and chemical properties of Al2SiO5. The Al3+ ions and O2−
ions migrate in the c direction with corresponding activation energies of 2.26 eV and 2.75 eV inferring
slow ion diffusion. The prominent isovalent dopants on the Al and Si sites are found to be the Ga
and Ge, respectively, suggesting that they can be used to prevent phase transformation and tune the
properties of sillimanite.
