Fig. 3: Transport calculations for para-NP single-molecule junctions based on the DFT+Σ approach.

a Transmission as a function of electrode displacement d and energy E. b Thermopower as a function of electrode displacement and Fermi energy E_F at T = 300 K. White areas correspond to values around 30 μV/K or above. The black solid line indicates vanishing thermopower and thus the positions of sign changes. Horizontal dashed lines in panel a mark the range of Fermi energies explored. c Overview of conductance values as a function of electrode displacement, showing the averaged and rescaled experimental data of Fig. 2 and the standard deviation as shaded area, DFT+Σ data using an electronic thermal smearing in the electrodes corresponding to T = 300 K, and DFT+Σ data employing an additional displacement and energy averaging with σ_d = 0.28 Å and σ_E = 0.11 eV. In the computations we set E_F = −5.3 eV, and each curve is aligned to the displacement d₀ with its respective conductance minimum. d Same as in panel c but for the thermopower. The displacement d₀ is fixed by the conductance. The inset in the upper left corner shows the extended central cluster used in the quantum transport calculations for d = 0 nm, near the destructive quantum interference dip. The Euclidean sulfur-sulfur distance amounts to 1.15 nm in this configuration. An animation of the stretching process as a function of displacement d is provided as Supplementary Movie 1.