In this study, we examine the interaction of Fc in the gas phase with Au(111) and Ag(111) surfaces, as these are the most stable surfaces for both metals. The method employed for constructing the metal surfaces follows the procedure outlined in our earlier work on Cyt/Au(111) and AzaCyt/Au(111). Specifically, the lattice parameter was optimized using a 12×12×1 Gamma-centered k-mesh. A dense fast Fourier transform (FFT) mesh and a high energy cut-off of 500 eV were used for the plane-wave basis set in all calculations. The firstorder Methfessel-Paxton (MP) method was employed with partial occupancy and a smearing width of 0.3 eV to ensure robust and efficient relaxation of the metal surfaces. The geometry optimization of the Au(111) and Ag(111) surfaces was conducted on free-standing (clean) metal slabs, as depicted in Figure . The surfaces were constructed using a slab model consisting of four Au(111) (or Ag(111)) layers in a periodically repeated 4×4 surface supercell, with each layer containing 16 atoms. The surface slabs were constructed with a 15 Å vacuum layer along the zdirection to eliminate interactions between adjacent supercells. All the four atom layers in the slab are fully optimised in the present study. The optimised lattice constants of Au(111) and Ag(111) surface slabs are 4.10 Å and 4.07 Å, respectively, which are in good agreement with previous measurements of 4.08 Å (Au) and 4.09 Å (Ag), respectively. In the optimization, the total energy convergence is 10 -4 eV and atomic relaxation < 0.015 eV/Å under the Hellmann-Feynman force convergence criteria.