Electronic and structural properties of the layered ternary carbide Ti₃AlC₂

The electronic and structural properties of the layered ternary compound Ti₃AlC₂ have been determined using the ab initio pseudopotential method based on density functional theory. We have obtained the equilibrium lattice parameters, the equilibrium atomic positions in the unit cell, and interatomic distances. The calculated bulk modulus is 190 GPa and is comparable to that of TiC. The band structure, density of states (DOS) and effective charges are presented and compared with those of TiC. The band structure indicates that Ti₃AlC₂ is an electronic conductor. The electronic structure discloses that the bonding in Ti₃AlC₂ is anisotropic and metallic-covalent-ionic in nature. Compare to the structure of TiC, the presence of Al changes the Ti-C-Ti-C covalent bond chain into a Ti-C-Ti-C-Ti-Al bond chain through its reaction with Ti, formingthe layered structure. Effective charge calculations suggest the ionic formula of Ti₃AlC₂ to be (Ti^1.18+)(Ti^0.59+)₂(Al^0.52-)(C^0.92-)₂.