Energies of the atomic steps formed on low-index surfaces of fcc metals

The energies of the steps formed by (a/2)[110] dislocations on the three low-index surfaces of silver and aluminium have been computed using many-body potentials. The 'tension' step is found to have an energy larger than the 'compression' step of the same atomic configuration and the energy difference is equal to the surface energy per atomic area. More generally, the energy difference between two glide steps having the same atomic configuration is simply the surface energy associated with the difference in length scale of the surfaces of two samples containing the steps. It follows that an intrinsic energy characteristic of the atomic configuration, independent of the mode of creation of the step, can be defined. Finally, the concept of intrinsic energy is discussed for growth steps and other steps formed by diffusion.