Transition metal dichalcogenide

Transition metals

Transition metal dichalcogenides typically adopt either cadmium diiodide or molybdenum disulfide structures. In the CdI₂ motif, the metals exhibit octahedral structures. In the MoS₂ motif, which is not observed for dihalides, the metals exhibit trigonal prismatic structures. The strong bonding between the metal and chalcogenide ligands, contrasts with the weak chalcogenide—chalcogenide bonding between the layers. Owing to these contrasting bond strengths, these materials engage in intercalation by alkali metals. The intercalation process is accompanied by charge transfer, reducing the M(IV) centers to M(III). The attraction between electrons and holes in 2D tungsten diselenide is 100s of times stronger than in a typical 3D semiconductor.