First-principles characterization of the structure and electronic structure of α-S and Rh-S chalcogenides

We have used first-principles calculations to study the structural, electronic, and thermodynamic properties of the three known forms of Rh-S chalcogenides: Rh2 S3, Rh3 S4, and Rh17 S15. Only the first of these materials of interest for catalysis had been studied previously within this approach. We find that Rh17 S15 crystallizes in a Pm 3̄ m centrosymmetric structure, as believed experimentally but never confirmed. We show band structures and densities of states for these compounds. Finally, we also investigated the ground-state structure of solid sulfur (α-S), one of the few elements that represents a challenge for full first-principles calculations due to its demanding 128-atom unit cell and dispersion interactions between S8 units.