Speaker
Description
The platinum group elements (PGEs) exist in different structures which are known and studied to some extent. The existence of these PGEs in pentlandite-like structure is a promising host phase of these PGEs. In this study Viena Ab-initio Simulation Package (VASP) density functional theory code was used to investigate phase stability of the PGEs, M9S8 (M = Ru, Pd, Os, Pt, Ir and Rh), pentlandite-like structures. The phase stability was investigated by calculating heat of formation, elastic properties, density of states (DOS) and phonon dispersion curves. The calculated heats of formation predicted that the stability decreased as: Os9S8 > Ru9S8 > Ir9S8 > Rh9S8 > Pt9S8 > Pd9S8. These indicated that the formation stability increases with an increasing period and decreasing group on the periodic table. Elastic properties of these pentlandite-like systems were calculated and we found that Rh9S8, Ir9S8, Pd9S8 and Os9S8 were mechanically stable, whereas Pt9S8 and Ru9S8 were unstable. The density of state of Ru9S8 and Pt9S8 appeared to have high contribution of electrons at Fermi level which suggested that Ru9S8 and Pt9S8 are unstable. The partial density of states showed that the atoms at tetrahedral sites lower the stability in the pentlandite-like systems. The phonon dispersion curves indicated that Os9S8, Ir9S8 and Rh9S8 have no negative modes at the gamma point suggesting stability, while the other structures are unstable. Thus the Os9S8, Ir9S8 and Rh9S8 are the most stable phases. These findings provided new knowledge that established the stability of the PGEs existence in a pentlandite-like structure that could be applicable in geological search of such phases.
