in tetrahedrally and octahedrally coordinates structures

Ultrawide-band gap (UWBG) semiconductors (band gap > 4 eV) have many potential interesting applications, such as in high-power electronics and deep-UV optoelectronic devices. LiAlO₂ is a candidate material for UWBG semiconductors. This project is a first-principles electronic structure study of LiAlO₂, focusing on band gap/band structure, bulk moduli of common crystal structures, and transition pressures between different structures. Specifically, we compare the tetragonal γ and orthorhombic β structures (both tetrahedrally coordinated) with the R-3m α structure and a disordered rocksalt type δ structure (both octahedrally coordinated). We calculate these properties using the density functional theory (DFT)-based linearized muffin tin orbital (LMTO) and pseudopotential plane wave methods, as well as the more accurate quasiparticle self-consistent GW (QSGW) approach. We find that the tetrahedrally bonded structures have slightly lower energy than the octahedral ones and a transition to the octahedral phase occurs near 2 GPa.