First-principles investigation on the structures, energies, electronic and defective properties of Ti 2 AlN surfaces

Abstract

In this research work, the structures, energies, electronic and defective properties of (0001),(101¯0),(112¯0) and (101¯3) surfaces of Ti2AlN were investigated systematically by the first-principles calculations based on density functional theory. The (0001) and (101¯0)are polar surfaces and have different kinds of surface terminations, while the(112¯0) and(101¯3) are non-polar surfaces. The calculated results show that the Ti(Al)-, Al- terminated (0001) surfaces experience the least relaxation, and N- terminated (0001) surface experiences the greatest relaxation. The calculated surface energies of non-polar surfaces are independent on the constituent element chemical potential, while surface energies of polar surfaces are correlated with the constituent element chemical potential. It is found that the (0001)-Ti(Al), (0001)-Al,(101¯0) -TiAl and (101¯3) surface are stable under the condition of Ti- and Al- rich environments, the (0001)-N surface is the most stable one under the Ti- and Al- poor condition. The electronic structures of all the surfaces except(101¯3) are significantly influenced by structure relaxations. Furthermore, the monovacancy formation energies on the surface layer are lower than that in the bulk, the monovacancies are most difficult to exist on the(101¯3) surface among all the surfaces.