LAUSR

In this study, we highlight the benefits and limits of using density-functional tight-binding (DFTB) with respect to standard density functional theory (DFT). The DFTB method is found to reliably reproduce the DFT adsorption energies and geometries. Overall, our results suggest that DFTB is a good reference method to set the correct chemical states and the initial geometries of proline interacting with gold cluster. The frontier orbitals energies suggest that in proline–gold cluster complex, the proline molecule can only act as an electron donor and the gold cluster as acceptor. The analysis of the electronic properties for arginine, arginine dipeptide, and TAT peptide which underline the role on the interaction of the s-like H states with the d-like Au states produces both bonding and anti-bonding occupied orbitals, and the process is well described by a model for the interaction of localized orbitals with narrow-band dispersive electron states. The bonding orbitals well below the metal Fermi level contribute to the adsorption of arginine, arginine dipeptide, and TAT peptide on gold.