Interaction of metal atoms with organic thin film is a fundamental issue to optimize performancesof novel devices. The computational investigations, based on density functionaltheory, reveal that a realistic description of the reactive processes is obtained whenthe organic thin film is modelled by its crystallographic structure.In this case, the metal atoms can react with multiple organic molecules present inthe solid forming complexes where they are bound both to O atoms and to aromatic Catoms of the molecules.Calculated band gap states, induced by chemical reaction upon deposition, reproducequite well the measured density of states as a function of the metal concentration inthe solid.Simulated core level shift spectra for N(1s), O(1s), Al (2p), in doped systems, are ingood agreement with experimental spectra and the electronic structure analysis providesa microscopic description of reaction processes.Interestingly, K atoms in PTCDA solid are ionically bound to anhydride O atoms andare able to form quasi mono-dimensional chain along the stack direction of the organicmaterial
