First-principles calculations on Ti2AlB2, Ti3AlB4 and Ti4AlB6, three potential new members of the orthorhombic MAB phase

MAB phases represent a class of ternary layered transition metal borides that are structurally analogous to the well-established MAX phase, and they exhibit promising potential in various applications, including mechanics, catalysis, wave-absorption, batteries, and high-temperature environments. However, only a few MAB phases have been experimentally synthesized, making the exploration of new phases a pressing challenge. In this study, three potential Ti-based MABs (Ti2AlB2, Ti3AlB4 and Ti4AlB6) are predicted via first-principles calculations and density functional theory (DFT). The computational analyses confirm the thermodynamic and mechanical stability of these phases, with their lattice parameters determined, providing valuable references for future experimental endeavors. Crystal structure analysis reveals a distinctive feature of MABs, the B-B zigzag chains, which are absent in MAX phases, endowing them with superior in-plane strength. Mechanical analyses show that these compounds exhibit elastic anisotropy, which is closely related to the microstructure of Ti-B slices. Electronic studies confirm the metallic nature of these compounds, while the highly reactive Al atomic layer suggests a significant potential for selectively etching to yield two-dimensional (2D) MBene. Optical studies indicate that these compounds possess excellent polarization and dielectric loss capabilities, making them promising candidates for next-generation materials in photo-thermal conversion, sensing and wave-absorbing devices.