Efficient supercell design for surface and interface calculations of hexagonal phases: α-Al2O3 case study

Challenges in modelling of surface and interfaces of non-cubic materials are addressed in this work. For hexagonal and rhombohedral crystals, the orthorhombic description introduced here enables efficient supercell design for modelling (0 0 0 1), (1 1 −2 0) and (1 −1 0 0) surfaces and interfaces. In this work, surface relaxations and energies of α-Al2O3 (0 0 0 1), (1 1 −2 0) and (1 −1 0 0) have been studied by ab initio calculations using the orthorhombic description. Excellent agreement with previously reported theoretical and experimental data confirms the reliability. Since this orthorhombic description involves purely geometrical transformation, this approach may enable a more efficient treatment of other phases of hexagonal symmetry.