Fig. 3.
Density of states projected onto the thiol group and the individual pyrimidine rings for a monolayer consisting of molecules with 7 repeat units plotted alternatingly in black and grey to improve visibility; the molecular structure at the top of the plot serves as guide to the eye and the left vacuum energy VLleft (cf. Fig. 4) is set to zero. The dash-dotted horizontal gray line indicates the energy of the highest occupied state. In addition, the rightmost curve shows the total DOS. Real-space representations of the lowest unoccupied and highest occupied peaks are depicted. The latter includes two crossing bands (as evidenced also by the higher associated DOS), one being derived from a σ- and the other from a π-orbital. This also results in the mixed σ- and π-character in the real-space representation. Note that this near-degeneracy might be a consequence of an orbital-dependent self-interaction error mentioned in the ‘Methods’ section [10].