Selfconsistent LMTO calculation for semiconductor clean surfaces

Abstract

We show that reliable selfconsistent densities of states and energy bands at the semiconductor-vacuum interface can be obtained by the all-electron linear muffin-tin orbitals (LMTO) method in the atomic sphere approximation (ASA). Our calculation is based on the empty sphere technique, i.e. interstitial spheres with zero atomic number, firstly introduced to well describe within the muffin-tin potential approximation the behaviour of solids with low coordination number, like group IV semiconductors. We show that the semiconductor-vacuum interface can be well described if the semi-infinite vacuum region is simulated by a semi-infinite empty sphere solid. The calculation is firstly applied to the Si(111)(1 × 1) surface, but its extension to more complex systems, like ultrathin overlayer chemisorbed structures, is simple. In this all-electron approach important data like surface core level energy shifts are easily obtained. Furthermore recent developments of the LMTO method, like transformation in a tight-binding basis, can be used to obtain nonspherical surface charge density plots and accurate total energies.