We present a method based on graph theory for the evaluation of the inelastic propensity rules for molecules exhibiting complete destructive quantum interference in their elastic transmission. The method uses an extended adjacency matrix corresponding to the structural graph of the molecule for calculating Green’s function between the sites with attached electrodes and consequently states the corresponding conditions the electron-vibration coupling matrix must meet for the observation of an inelastic signal between the terminals. The method can be fully automated and we provide a functional website running a code using Wolfram Mathematica, which returns a graphical depiction of destructive quantum interference configurations together with the associated inelastic propensity rules for a wide class of molecules.
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Very recently, two works14,16 have addressed in detail general questions concerning the DQI origin, predictability, and classification.
For example, we ignore the chemical instability of cyclobutadiene represented by the square graph in Fig. 6, which we use just for the illustration of our points.
Since Fano resonances often occur to a side from other extrema, they often have an asymmetric-in-energy signature. Not so it happens, however, in our case.