Structural representation of the Violet Lander (CH) along different direction views. The experimental and theoretical values of the major molecular dimensions L and W are displayed in Table 1 (see text for discussions).
STM snapshots from the scanning of VL molecules adsorbed on Cu(110) surface. (a) and (b) Molecules with their main boards aligned with the  direction (labeled 1) do not diffuse; molecules rotated by 70 (labeled 2) are able to diffuse along the  direction. In the upper panels are showed zoomed images of rectangular sections of (a) and (b), respectively. (c) and (d) 3D-graphical atomistic representation of the VL in its (c) aligned and (d) 70 rotated configurations with respect to the  Cu(110) surface direction. The STM images represent raw data, no image processing was done after acquisition.
Relative total energy profile of a VL molecule deposited on a Cu(110) surface as a function of the angle between the main axis of the molecule and the  direction (see Fig. 2). For each angle, the molecule is optimized with its board or central ring being frozen.
Relative total energy profile of a VL molecule deposited on Cu(100) and Cu(111) surfaces as a function of the angle between the molecule main axis and the  and 1] directions, respectively.
Energy profile for the VL molecule displacement onto the Cu(110) surface, along the  direction in the rotated and nonrotated geometries.
Force profile, as a function of time, as a result of the interaction between the VL molecule in the (a) nonrotated and (b) rotated geometries, and the Cu(110) surface. Times corresponding to 1.8, 4.8, and 15 ps as a result of the initial impulse are shown by arrows.
Root mean displacement (RMD) of rotated (dot pointed curve) and nonrotated (fill curve) VL. The diffusion coefficient associated from curves are cms and cms for nonrotated and rotated VL, respectively.
Schematic view of a VL molecule in its (a) nonrotated and (b) 70 rotated configurations with respect to the  Cu(110) surface direction. Insets 1 and 2 show structural details of the hydrogen atoms fitting into the hollow sites of the Cu(110) surface, in the nonrotated geometry. When the board slides, the legs rotate easily around the sigma bonds (σ) inducing the hydrogen atoms (H) to remain in the hollow sites.
Schematic view of the VL molecule for the nonrotated configuration on (a) Cu(100) and (b) Cu(111) surfaces, respectively. The different hydrogen atom orientations in relation to the Cusurface atoms are clearly visible. Insets 1 and 2 show detailed views of the poor matching between the hydrogen atoms at the bottom of the legs and the hollow sites of Cu(100) and Cu(111) surfaces,respectively. In comparison with the Cu(110) (Fig. 8), the hollow sites of Cu(100)and Cu(111) are shallower.
Violet Lander dimensions (Fig. 1), in angstrom, optimized with classical molecular mechanics [universal force field (Ref. 39)], semiempirical AM1 method (Ref. 46), DFT-LDA-Siesta (Refs. 47 and 48), and DFT-LDA-DMol (Refs. 49–51).
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