Quasiparticle electronic and optical properties of the Si-Sn system. 
The Si(1-x)Sn(x) material system is an interesting candidate for an optically active material compatible with Si.  Based on density functional theory with quasiparticle corrections we calculate the electronic band structure of zinc-blende SiSn under both compressive and tensile strain.  At 2.2% tensile strain the band gap becomes direct with a magnitude of 0.85 eV. We develop an accurate tight-binding parameterization of the electronic structure and calculate the optical properties of SiSn.  Furthermore, the silicide SiSn(2) is investigated and found to have metallic character.