Single-Metal-Atom Chains at Mirror Twin Boundaries in Transition Metal Dichalcogenides: Electronic, Magnetic, and Catalytic Properties

The experimentally realized atomic chains composed of transition metal atoms embedded into mirror twin boundaries (MTBs) in two-dimensional MoS₂ represent a class of quasi-one-dimensional systems with intriguing magnetic and electronic characteristics. By employing first-principles calculations, we investigate the possibility of creating single-metal-atom chains (SMACs) in other Mo- and W-based H-phase transition metal dichalcogenides. Our results indicate that for the transition metal atoms with the number of d-electrons different from that in Mo and W, the formation of SMACs is energetically preferable over having isolated substitutional impurities in the basal plane of the TMDs, pointing out that these structures can be synthesized. We further study the magnetic and electronic properties of these systems and demonstrate that many structures exhibit half-metallic electronic behavior associated with a Peierls-like distortion and thus can be employed in spintronic applications. Finally, we investigate the potential of various SMACs to be used as a catalyst in the hydrogen evolution reaction (HER). Our calculations predict that some of the SMACs should exhibit HER activity comparable to or even superior to that of the standard Pt(111) surface.