Tailoring Band Gap and Hardness by Intercalation: An ab initio Study of I8@Si-46 and Related Doped Clathrates

We present an ab initio study of the structural and electronic properties of the recently synthesized I8@Si-46 clathrate which is shown to be a degenerate p-type doped system. The intercalation significantly opens the band gap to a 1.75 eV value within the density functional theory. We study further the intercalation by other neighboring elements. A quasiparticle study reveals that such systems can display a band gap in the “green-light” energy range. Finally, we show that the bulk modulus can be increased to values equivalent to the one of the diamond phase.