Ab initio study of the Cr₂ AlC (0001) surface

Using an ab initio total energy method, we have calculated the surface energy and surface stress of Cr2 AlC (0001) with the configuration of the top layer as Al [(0001) Al], Cr [(0001) Cr], and C [(0001) C] atoms, respectively. Both the surface energy and surface stress of (0001) Cr are very close to (0001) C. While those of (0001) Al are the lowest, suggesting that this surface configuration is the most stable one. Furthermore, the interplanar relaxation does not have any obvious effect on the surface energy, while the surface stress decreased dramatically under layer relaxation. The Cr-C bond length in the surface layer contracted by >5%, and the bond contraction for Cr-Al is <1.5%, showing that the bond strength in the surface layer is higher than that in the bulk region.