The Electronic Properties of Cu 2 CoSiS 4 , Cu 2 CoGeS 4 , and Cu 2 CoSnS 4 : A DFT Approach

Abstract

Cu2CoSiS4, Cu2CoGeS4, and Cu2CoSnS4 crystallize in the stannite (I-42m) structure, and their electronic properties have been investigated by the pseudopotential method within the framework of the density functional theory (DFT). The LDA+U technique and the projector augmented wave (PAW) were employed in the computations. The results of the calculations showed these materials are metallic with pseudo band gap. The respective pseudo band gap for Cu2CoSiS4, Cu2CoGeS4, and Cu2CoSnS4 are 1.52 eV, 2.96 eV, and 1.2 eV. The isolated subband at the Fermi level for Cu2CoSiS4 are of Co-3d states, the Si-3s and Si-3p states are the dominate states in the conduction band. The top of the valence band of Cu2CoGeS4 is predominately of the S-3p and Ge3d states, while the bottom of the conduction is majorly of Ge-3d and Ge-4s states. For Cu2CoSnS4 compound, the valence band top is majorly of S-3p; and the conduction band is of Sn-5s and Co-3d.

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