Atomic and electronic structures of I-V-VI2 ternary chalcogenides

Atomic and electronic structures of I-V-VI2 (I = Na, K, Ag, Cu, Au; V = As, Sb, Bi; VI = S, Se, Te) are studied using first-principles hybrid density functional calculations. We find that the strong hybridization between the trivalent cation (As, Sb, and Bi) p states and the divalent anion (S, Se, and Te) p states tends to introduce electronic states in the band gap or pseudogap region and drive the systems toward metallicity. The atomic ordering on the cation sublattice of the ternary chalcogenides, therefore, has a strong impact on the energetics and the electronic structure in the neighborhood of the Fermi level as it determines if a certain atomic configuration is favorable to the highly directional cation p–anion p interaction. Besides these p states, the s state (in the case of Na and K) or the s and d states (Ag, Cu, and Au) can also play an important role in the band-gap formation. Our study suggests how to manipulate the electronic structure of these ternary compounds such that they show desired features for different applications by modifying their atomic structure and/or by changing their constituent element(s).