Phase stabilities at a glance II: Ternary ordering variants of pyrite and marcasite type structures

There is a solid history of theoretical and experimental studies of pyrite- and marcasite-like systems that primarily occur for dipnictide and disulfide systems of late transition metals. Ordered mixed occupation of the anionic sites of these compounds results in a multitude of different ternary structures. A full set of possible combinations is presented here including all experimentally known structure prototypes. They are part of a series MPnS (M = Fe, Co, Ni; Pn = As, Sb) that is investigated in terms of recently established stability diagrams with decomposition lines. In contrast to the respective binary systems, significantly lower differences in cohesive energies and cell volumes have to be dealt with particularly for related ordering variants. Due to sufficient experimental data on hand, the accuracy of the GGA-based density functional theory calculations can be estimated within the marginal ranges in order to allow for reliable predictions of new phases of these and many other related systems.