Electronic structure of the Nowotny chimney-ladder silicideRu2Si3s

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We report ab initio calculations for the electronic structure of the Nowotny chimney-ladder silicide ${\mathrm{Ru}}_{2}$ ${\mathrm{Si}}_{3}$ in the orthorhombic low-temperature phase. We find ${\mathrm{Ru}}_{2}$ ${\mathrm{Si}}_{3}$ to be a semiconductor with a direct band gap of about 0.45 eV. Since this gap is a p-d gap, the oscillator strength for a direct transition is expected to be of sizable magnitude. Also, the calculated effective masses of hole and electron states suggest that ${\mathrm{Ru}}_{2}$ ${\mathrm{Si}}_{3}$ is a very promising material for various applications in semiconductor technology. The electronic structure is controlled by the hybridization of Si p states with Ru d states and shows similarities to the group-IV transition-metal disilicides (${\mathrm{CrSi}}_{2}$ , ${\mathrm{MoSi}}_{2}$ , ${\mathrm{WSi}}_{2}$ ) and to transition-metal-rich silicides. The calculations are based on the density-functional theory in local-density approximation and are performed by means of the full-potential linearized-augmented-plane-wave method.