We present a theoretical study of the adsorption of benzene C 6 H 6 on the Cu(100) metal surface. The insulating effect of ionic films on this system has also been investigated by adsorbing C 6 H 6 on the same surface covered with 1, 2, and 3 monolayers of NaCl. For this purpose, we employed density functional theory (DFT) including the van der Waals dispersion forces via a DFT-D2 scheme. For all the studied systems we analyzed the adsorption energies and geometries as well as the density of states in order to get a complete description of the type of binding, the charge transfer between the molecule and the surface, and the electronic level alignment after adsorption. We show that the molecule−substrate interaction is weak and mainly governed by dispersion forces, with an almost insignificant charge transfer between the substrate and the adsorbate. We found a progressive decoupling of the molecule from the metal surface when the size of the ultrathin insulating NaCl film increases.

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Organic charge transfer (CT) compounds display a wide range of exotic electronic properties (charge-density wave stabilization, Peierls transitions, etc.) depending on the amount of charge transferred from the donor (D) to the acceptor (A) species. A complete exploration of the complex electronic phase diagrams for such compounds would thus require methods to systematically tune the amount of charge exchanged in the CT process. This has proven however challenging in the past: chemical functionalization of the constituent molecules can also affect the packing of the molecular units in the crystal, whereas changing D:A stoichiometry is often not possible in the bulk. Interestingly, it was recently found that multiple stoichiometries can actually be achieved by codeposition of different amounts of D and A molecules on metal surfaces. The question, however, of whether CT processes between D and A molecules can be tuned with the D:A ratio in such mixtures has not yet been studied, and it is no trivial matter, since competing CT processes between the metal surface and the organic adsorbates might hinder interadsorbate charge transfer. Here we demonstrate that the CT process from the organic donor tetrathiafulvalene (TTF) to the acceptor tetracyanoquino-p-dimethane (TCNQ) can be tuned with exquisite accuracy (∼0.1 e − ) by controlling the stoichiometry of D:A cocrystals deposited on Ag(111). This control opens new avenues to explore the complex phase diagrams of organic CT compounds and to tailor their electronic properties.

We present a theoretical study on the adsorption of acrylonitrile (ACN) on the Cu(100) surface. In order to check the insulating effect of an ionic film, we have also studied the adsorption of the acrylonitrile on the same metallic surface previously covered with one, two, and three NaCl monolayers. For this purpose, we have employed the density functional theory (DFT) including van der Waals dispersion forces via a DFT-D2 scheme. For these systems, a thorough ab initio molecular dynamics and static DFT study is presented. We have analyzed adsorption energies and geometries, and also explored the electronic structure and the charge transfer between the molecule and the surface. We have as well studied the potential energy surface of each system. From the dynamic point of view, several trajectories at different temperatures and conditions have been studied, in order to get an accurate description of the stability when ACN is adsorbed on the surface at a certain temperature. The studied systems present a weak interaction between the substrate and the adsorbate. Tendencies and common behaviors are presented as well as the different behavior of the ACN/2NaCl/Cu(100) system compared with the others.

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In this work we present a density functional theory study of the interaction between a positively charged exohedral metallofullerene and several hydrogen molecules.

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