Electronic structure and bonding properties of layered machinableTi2AlCandTi2AlNceramics

Abstract

The electronic structure and chemical bonding of the layered ternary compounds ${\mathrm{Ti}}_{2}\mathrm{AlC}$ and ${\mathrm{Ti}}_{2}\mathrm{AlN}$ have been calculated by the ab initio pseudopotential total-energy method. The results show that ${\mathrm{Ti}}_{2}\mathrm{AlC}$ and ${\mathrm{Ti}}_{2}\mathrm{AlN}$ exhibit metallic electrical conductivity with an anisotropic character and ${\mathrm{Ti}}_{2}\mathrm{AlC}$ should be more conductive than ${\mathrm{Ti}}_{2}\mathrm{AlN}.$ The chemical bonding in ${\mathrm{Ti}}_{2}\mathrm{AlC}$ and ${\mathrm{Ti}}_{2}\mathrm{AlN}$ 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.