Figure 1: Model of rotational defect in graphene and TMDs.
From: Three-fold rotational defects in two-dimensional transition metal dichalcogenides

(a) Atomic model of graphene. (b) Top view of the Stone–Wales transformation, showing 90° rotation of a carbon bond. (c) Atomic model of graphene with a divacancy. (d) The atomic model of SW-transformed graphene divacancy. (e) Atomic model of TMDs with a structural formula MX2, the top view. The orange spheres represent chalcogen atoms, the blue ones the metal atoms. (f,g) Triple M–X bonds showing 60° rotation from the top and perspective views. (h) The atomic model of trefoil defect. Three M–X bond pairs marked by blue bars are 60° rotated from those in e. (i) A typical ADF image of WSe2 observed at 500 °C. The density of trefoil defect is found to be about 5.1%. Scale bar, 2 nm. (j) The magnified ADF image from the black square in i. Scale bar, 0.5 nm.