Exploration and investigation of stable novel Al2O3 by high-throughput screening and density functional theory

The graph and group theory based random strategy (RG2) code is employed to obtain three stable Al2O3 polymorphs (P21/c, Pnma-I, and Pnma-II Al2O3) are obtained based on high-throughput screening and density functional theory. The three Al2O3 polymorphs have dynamic stability, mechanical stability, and thermal stability and can remain thermally stable at least up to 2000 K. As the pressure increases, P21/c Al2O3 changes to CaIrO3-type Al2O3 at ∼75–80 GPa. The electronic band structures show that the three polymorphs are all ultrawide band gap semiconductor materials with band gaps of 5.74–6.40 eV, and P21/c Al2O3 has a direct band gap. The B/G values of P21/c and Pnma-I Al2O3 are greater than 1.75, which confirms that they are ductile. They may have potential application in optoelectronic material, microelectronic material, and thermal barrier coating materials.