Electronic structure, surface states, surface energy, and work function of the Cu(100) surface

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Abstract
The modified augmented-plane-wave (MAPW) method is adapted for film geometry. Emphasis is especially put on the choice of the trial functions to achieve high accuracy for the Bloch state as well as for the self-consistent potential in the local-density approximation. Results obtained for one-, three-, five-, and seven-layer Cu(100) films are found to be in good qualitative agreement with other investigations. However, a more precise comparison with recent investigations shows some deviations which are outside the range of accuracy characteristic for a method. At X¯ and M¯ surface states are found which are more or less close to the experimental results. The density of states and the electronic charge in the middle of the seven-layer film are only slightly different from the corresponding magnitudes in the bulk evaluated by use of the MAPW method with similar computational parameters. With increasing number of layers the work function approaches the margin of the experimental values. As the total energy of the films turns out to be proportional to the number of layers a reasonable value of the surface energy could be given. For the electric field gradient a value was obtained which is by about a factor of 3 smaller than its experimental value. This is due to the fact that in the present calculation the effective potential is assumed to be spherical within the muffin-tin spheres.