Tailoring band gap and hardness by intercalation: An ab initio study of I-8@Si-46 and related doped clathrates

Abstract

We present an ab initio study of the structural and electronic properties of the recently synthesized I-8@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.