Description of DFT calculations
All DFT calculations were performed using the real-space projector augmented
wavefunction (PAW) method as implemented in the GPAW software package (18,19).
We employ the local density approximation (LDA) (17) to the exchange and correlation
(xc)-functional. Note that differences between the energetics obtained within the local
density approximation (LDA), generalized gradient approximation (GGA), or rangeseparated
hybrid xc-functionals are expected to be an order of magnitude smaller than the
energy of the most weakly bound transition state relative to the reactant following the
initial cyclization for each reaction pathway. Further, the LDA often provides superior
bond length and geometry predictions compared to more computationally expensive
methods, such as GGAs and hybrids. This suggests that LDA results are sufficiently
accurate for describing the chemical processes under consideration (32).
We perform Γ point calculations using a grid spacing of h = 0.2 Å, an electronic
temperature of kBT = 0.1 eV with all energies extrapolated to T = 0 K, and relax all
molecular structures until a maximum force below 0.05 eV/Å is obtained. Adsorption on
the Ag(100) surface is modeled using a 6×6×3 slab fixed to the experimental coordinates
obtained from a lattice parameter for Ag of 4.09 Å, and including more than 12 Å of
vacuum between the molecular layer and the repeated image of the Ag(100) slab. The
6×6×3 slab provides at least 4 Å of separation between repeated molecular images in the
surface plane. We find these values are sufficient to converge both energy differences and
the electron density for the systems under consideration.