Electronic structure and bonding properties of layered machinable Ti2AlC and Ti2AlN ceramics

The electronic structure and chemical bonding of the layered ternary compounds Ti2AlC and Ti2AlN have been calculated by the ab initio pseudopotential total-energy method. The results show that Ti2AlC and Ti2AlN exhibit metallic electrical conductivity with an anisotropic character and Ti2AlC should be more conductive than Ti2AlN. The chemical bonding in Ti2AlC and Ti2AlN is also anisotropic and is metallic-covalent-ionic in nature. On the basis of total-energy estimation we conclude that the replacement of C by N will result in a stabilization of the hexagonal structure and decrease in metallic properties.