Fig. 6. The mean hydrogen bond lengths for each stationary point in the stepwise double proton transfer reaction in GC. The geometries for each stationary point are optimised using B3LYP+XDM/aug-cc-pvdz/AMBER. The bonds being broken (N4–H4 and N1–H1) are highlighted in purple, and the bonds that are formed (O6–H4 and N3–H1) are highlighted in green. The external electric fields (E+x in red and E−x in blue) are applied at 1.00 × 109 V m−1, and no field (E0) is given in black. The error bars are the standard deviation of the mean bond lengths.
