fig1

Figure 1. (A) The general MX₂ formula of TMDs and the periodic table distribution of the transition metal (M) and chalcogen (X) elements forming the structure. Non-layered structures were identified for the M elements (Co, Rh, Ir, and Ni), which are indicated by half-colored boxes, whereas fully colored boxes represent layered structures, adapted with permission^[46]. Copyright 2015, Springer Nature Link; (B) schematic representation of the basic electron energy diagram of octahedral and trigonal prismatic coordinate transition metals, adapted with permission^[47]. Copyright 2021, Elsevier B.V.; (C) representative crystal structure of MoS₂ and WS₂: Octahedral (1T), Trigonal prismatic (2H) and Trigonal prismatic (3R) polytypes, adapted with permission^[48]. Copyright 2017, Royal Society of Chemistry.