Surface states at the (001) surface of CuAuI

We report calculations of the electronic structure in the neighborhood of the (001) surface of CuAuI using the self-consistent-field, linear muffin-tin orbital method within the atomic sphere approximation, with a slab geometry and including the surface dipole terms. We focus our attention on the vicinity of the (M) over bar point in the surface Brillouin zone and we identify the two (Tamm-type) surface states reported recently in photoemission measurements. The overall agreement between the theoretically determined dispersions of these states and those observed experimentally is very good and provides strong support for our calculational scheme. We show also that measurements of the surface core level shifts should allow a determination of the termination.