Figure 5.
Contact gepmetries. A-D show contacts of nearly equivalent energy for which the ΔGON vs. GBL curves in Figure 4 were calculated. E1-E8 demonstrate an intrinsic instability in the surface bonding as a function of the tunnel gap size (note the differences between the two configurations circled in red). Note also how the molecule remains “stretched” (4,5 relative to 1,8) even after the bond to the electrode is “broken”, a configuration that is presumably not available to stiffer molecules.