First-principles studies of the effects of vacancy defects on the properties of Ta2AlC

The effects of vacancy defects on the structural, electronic, mechanical, thermal and optical properties of Ta2AlC MAX-phase were investigated by density functional theory (DFT). The formation enthalpy and elastic properties indicate that all the structures in this calculation are thermodynamically and mechanically stable. The absence of atoms in Ta2AlC weaken the stiffness of the material, improve the plasticity, reduces the thermal conductivity and change the anisotropy of elastic and thermal conductivity. The Ta2AlC has a strong C-Ta covalent bond. The vacancy of Al atoms has no effect on the C-Ta bond, but the VTa, VC weaken the covalent bond severely. The vacancy defects improve the optical conductivity and reflectivity of the Ta2AlC in low energy region.