A first-principles study of MgB2 (0001) surfaces

Abstract

We report self-consistent {\it ab initio} calculations of structural and electronic properties for the B- and Mg-terminated MgB${}_2$ (0001) surfaces. We employ ultra-soft pseudopotentials and plane wave basis sets within the generalized gradient approximation. The surface relaxations are found to be small for both B- and Mg-terminated surfaces. For the B-terminated surface, both B $\sigma$ and $\pi$ surface bands appear, while only one B $\pi$ surface band exists near the Fermi level for the Mg-terminated surface. The superconductivity of the MgB${}_2$ surfaces is discussed. The work function is predicted to be 5.95 and 4.25 eV for the B- and Mg-terminated surfaces respectively. The simulated scanning tunneling microscopy images of the surfaces are not sensitive to the sign and value of the bias voltages, but depend strongly on the tip-sample distance. An image reversal is predicted for the Mg-terminated surface.

3 pages, 4 figures, Revtex