Fig. 2.
Analyses of stable edge structures formed during in situ heating. a–d Experimental (the 1st row) and simulated (the 2nd row) HAADF-STEM images, as well as corresponding atomic models (the 3rd row) and local density of states (LDOS) with arbitrary unit (the 4th row) of ZZSe-Mo-NW30 (a), ZZSe-GB4-Se (b), ZZMo-NW30 (c), and ZZMo-Se (d) edges, respectively. Fermi energy in LDOS is set to be 0. Red and black LDOS plots are calculated from atoms framed by red and black dashed boxes, respectively. The isosurfaces (highlighted by blue surfaces) of 0.01 e/Å3 spin-magnetization density (Δρ = ρ↑ ‒ ρ↓ = 0.01 e/Å3) are overlaid on the atomic structure of ZZSe-Mo-NW30 in a. The other three edges have negligible spin-magnetization. Scale bar corresponds to 1 nm. e, f, DFT-calculated formation energy per unit length (Ef) as a function of the Mo chemical potential, µMo, for four Se-oriented (ZZSe) edges (e) and three Mo-oriented (ZZMo) edges (f). The two vertical dashed lines denote the range 0 eV < µMo < 2.04 eV, where MoSe2 can remain stable with respect to the formation of bulk Mo (µMo = 2.04 eV) or bulk α-Se (µMo = 0 eV). g LDOS of freestanding MoSe NW contributed by Mo (black) and Se (red) atoms