Entropy stabilization of two-dimensional transition metal dichalcogenide alloys: A density functional theory study

As high-entropy alloying provides an increasingly important avenue for widening the set of functional materials for a variety of applications, it is useful to uncover synthesis routes that do not rely on large temperatures for achieving entropic stabilization. Focusing on transition-metal dichalcogenides, we present direct computational evidence from density functional theory calculations that high-entropy disulfide (HES) alloys with five cations from groups 4-6 are thermodynamically stable at temperatures routinely achievable in conventional deposition systems. While all 126 sulfide combinations with five group 4-6 transition metals are thermodynamically favorable at low (< 800 K) or medium (< 1200 K) temperatures, we show that electronegativities, valence electron concentrations, and atomic radii of cations can help predict whether an HES alloy is stable in the 1-H or the 1-T structure. Furthermore, replacing one of the five cations with another, from outside groups 4-6, can still yield HES alloys with nearly planar layer morphologies and stabilization temperatures below 1200 K, albeit with some localized defects. These results demonstrate that a wide range of stable HES alloys can be synthesized experimentally as 2D layers, thereby providing facile ways for expanding the materials' space with potential applications in electrochemical devices, catalysis, energy storage, or sensing. Published under an exclusive license by AIP Publishing.

Automated summary

As high-entropy alloying provides new synthesis routes for functional materials, this study demonstrates computationally that stable high-entropy disulfide (HES) alloys can be achieved at low temperatures for potential applications. By analyzing various factors, such as electronegativities, valence electron concentrations, and atomic radii, the stability and structure of HES alloys can be predicted. Furthermore, replacing one of the cations can still yield stable alloys with some localized defects.