Figure 2.

a) Energy barrier and atomic structures during the transformation from the D _3d to the D _3h monolayer. The transition‐state (TS) structure is indicated. b) Fluctuations of the total potential energy of D _3d monolayer during the molecular dynamics simulation at 300 and 500 K, respectively. c) Phonon spectrum of the D _3d monolayer. d) Phonon spectra of δ(D _3d), ω(D _3d), and ϕ(D _3d). The shear and breathing mode branches are shown in red and blue, respectively.