Self-consistent energy bands in aluminum and electronic surface states and resonances on the (001) surface

The band structure of aluminum has been calculated self-consistently with the use of the Kohn-Sham-Gaspar local exchange potential and the linear combination of Gaussian orbitals method. The resulting band structure, using a basis set of 28 contracted Gaussian-type orbitals, is in excellent agreement with the previous work of Singhal and Callaway in which a basis set of 60 uncontracted Gaussian functions was used. After projection of the bulk bands onto the two-dimensional (001) surface Brillouin zone, surface states and resonances have been calculated along the $\overline{\Delta }$ line with the use of the Green's-function formalism. At point $\overline{\Gamma }$, the surface state is located 2.92 eV below $E_F$, in excellent agreement with the experimental result, 2.8±0.2 eV below $E_F$. In addition, a resonance is found 0.7 eV below $E_F$ with a half-width of 0.4 eV, hitherto interpreted only as Fermi edge intensity. From the midpoint of the $\overline{\Delta }$ axis moving onward up to the Fermi energy, the observed main peak is attributed to surface resonances.