Constant-area and fully-relaxed molecular dynamics methods were used to study the properties of the surface and point defects at, and near to, the {001} surfaces of bulk and thin-film materials. The surface tension was greater than the surface energy for all {001} surfaces in the sequence: Al (1005mJ/m2) < Ni3Al (mixed Ni-Al plane outermost, 1725mJ/m2) < Ni3Al (all Ni-atom plane outermost, 1969mJ/m2) < Ni (1993mJ/m2). At the surface of a bulk Ni3Al crystal with the mixed Ni-Al plane outermost, the Al atoms stood out by 0.0679Å as compared with the surface Ni atoms. At the all Ni-atom surface, the Al atoms in the second layer stood out by 0.0205Å as compared with Ni atoms in the same layer. The vacancy formation energies were equal to about half of the bulk values in the first layer, and reached a maximum in the second layer; where the atomic energy was close to the bulk value, but the change in embedding energy of neighboring atoms -before and after vacancy formation - was greater than that in the bulk. The vacancy formation energy and the surface tension suggested that the fourth layer was in a bulk state for all the surfaces.

Point-Defect Properties of and Sputtering Events in the {001} Surfaces of Ni3Al - I. Surface and Point-Defect Properties. Lai, W.S., Osetsky, Y.N., Bacon, D.J.: Philosophical Magazine, 2004, 84[2], 173-91