CORRELATION BETWEEN ENERGY, SURFACE-TENSION AND STRUCTURE OF FREE SURFACES IN FCC METALS

A many-body potential of the embedded-atom-method (EAM) type and a Lennard-Jones (LJ) pair potential are used to determine the zero-temperature structures, energies and surface tensions of 85 different free surfaces in fcc metals. The variation of the surface energy as function of the two variables characterizing the surface normal, n̂, is found to be similar for the two potentials. However, while the LJ potential yields outward relaxation of the surface plane in some cases and inward relaxation in others, the EAM potential yields inward relaxation for all surfaces considered. Large differences are also found in the magnitudes of the related surface tensions and in their dependence on the two degrees of freedom in n̂. These differences are shown to arise from the very different magnitudes of the perfect-crystal cohesive energies associated with the two potentials and from their rather different variations as function of volume. In spite of these differences, however, a strong correlation is found for both potentials between the number of broken nearest- and second-nearest neighbor bonds on the one hand, and the surface tensions and energies on the other. © 1990.