Spontaneous L1(2) order at Ni90Al10(110) surfaces: An X-ray and first-principles-calculation study
R. Drautz, H. Reichert, M. Fähnle, H. Dosch, J. M. Sanchez.
Physical Review Letters, 87, 236102 P, (2001)
We have combined x-ray diffraction studies with first-principles calculations to study the interplay between segregation and ordering at the (110) surface of Ni90Al10. We find a L1(2)-ordered monolayer at the surface. The observed ordering as well as recently reported Al segregation at the surface are explained in a consistent picture. A delicate competition between the tendency for Al segregation and ordering in the Ni-Al system induced by the symmetry break at the surface stabilizes a long-range ordered surface in the entire concentration range c(Ni) > 0.75,