Simulación de adsorción en superficies a partir de cálculos ab initio sobre nano-clusters de átomos de oro

We have studied a nanosystem consisting of an alpha helix thio-polypeptide of high dipole moment chemisorbed on a Au₂₃ cluster surface with sulfur as the linking atom. We have studied a particularly important geometry where the alpha helix is almost perpendicularly oriented with respect to the gold cluster surface for the two possible directions of the molecular dipole moment. We have performed an ab initio quantum chemical study of this system to determine some characteristic properties such as the electric dipole, spin density and electronic population (DOS) near the Fermi level. For the calculation of the surface DOS we have implemented a new methodology based on an algorithm developed by us to analyze the electronic density. Our results give some clues for the understanding of the changes in the DOS, and the appearance of electronic states with high magnetic moments, during the process of formation of self-assembled monolayers of thio-polypeptide molecules chemically inked to the surfaces of gold clusters. These processes are related to both chemisorption-induced magnetism and spin transport in these systems.