LiTiAlO4: A novel wide band gap semiconductor for optoelectronic and thermal management, insight from DFT and AIMD within HSE06

Abstract

LiTiAlO${}_4$ has a unique crystalline structure and combines lithium with transition metals. This study investigates the electronic structural, dynamic, thermal, and optical properties of LiTiAlO${}_4$ using advanced computational methods, including Density Functional Theory (DFT) with the HSE06 hybrid functional and Ab Initio Molecular Dynamics (AIMD). The material is very stable structurally, as shown by its negative formation energy of -3.226 eV and stable lattice parameters ($a=5.76$ $\text{Å}$, $b=5.92$ $\text{Å}$). The phonon dispersion analysis indicates that the material is stable over time, with no imaginary frequencies and a clear difference between the acoustic and optical phonon modes. The structure’s mechanical stability is confirmed according to fundamental elasticity theory. The phonon PDOS shows that oxygen dominates mid- and high-frequency modes, while lithium contributes at mid frequencies. These vibrations govern the temperature-dependent increase in heat capacity and decrease in thermal conductivity of LiTiAlO${}_4$. The low thermal conductivity is due to the enhanced phonon scattering rate within the structure, resulting from pronounced anharmonicity. The electronic band structure shows that it is a direct semiconductor with a wide bandgap of 4.82 eV (HSE06), which makes LiTiAlO${}_4$ a viable choice for ultraviolet (UV) optoelectronic uses. Its optical properties, such as its dielectric function, refractive index, absorption coefficient, and optical conductivity, show how well it can absorb light and create charge carriers. These findings collectively underscore LiTiAlO${}_4$’s suitability for advanced applications in optoelectronics, thermal management, and energy conversion technologies.