We analyze with the aid of density functional theory and molecular dynamics simulations the adsorption of sulfur (S) on a Au(111) surface at different temperatures with a variety of geometries. We have found a new superficial phase in which sulfur atoms form a quasi-linear chain with energies very close to the expected . The results suggest the coexistence of both configurations at T < 300 K. At high temperatures (T > 300 K) it was shown that the sulfur atoms have high mobility which allows their migration among different adsorption sites. At low temperatures, the mobility decreases and a thermal activation barrier of 25-30 meV can be estimated.

A controversy about the conductance through single atoms still exists. There are many experiments where values lower than the quantum unity G(0) = 2e(2)/h have been found associated to Kondo regimes with high Kondo temperatures. Specifically in the Pd single atom contact, conductance values close to G(0)/2 at room temperature have been reported. In this work we propose a theoretical analysis of a break junction of Pd where the charge fluctuation in the single atom contact is limited to the most probable one: [Formula: see text]. The projected density of states and the characteristics of the electron transport are calculated by using a realistic description of the interacting system. A Kondo regime is found where the conductance values and their dependence on temperature are in good agreement with the experimental trends observed in the conduction of single molecule transistors based on transition metal coordination complexes.

Theoretical results for the adsorption of half of a monolayer of S on Au(111) are presented. The simulations were made using a density functional theory (DFT) tight binding approach combined with classical molecular dynamics at 800, 500, 300, 150 and 1 K. By considering a minimal (2 × √3) unit cell, two stable adsorbed phases are found: a dimeric one and another forming a rhomboidal structure depending on the preparation of the sample at high temperatures. Optimized calculations at T = 0 K indicate that the stability of the dimeric phase is due to the increase of the binding energies between sulfur atoms. Enforcing previous results (Gómez-Carrillo et al 2011 Phys. Chem. Chem. Phys. 13 461) it is verified that at high temperatures (T > 300 K) sulfur atoms have a high mobility which allows migration among different adsorption sites. The mobility decreases with the temperature and, as in the previous work, a thermal barrier of 25-30 meV is found. On enlarging the unit cell new agglomerates are found, in good agreement with experimental data.

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Recent developments in the field of nano-electronics have encouraged the study of quasi one dimensional systems such as DNA and its applications to new devices. In this work we use two models to explore the vibrational properties of DNA-like chains: a linear chain and two laterally coupled linear chains. In the former case, the disorder induces a diatomic behavior, while monoatomic characteristics are displayed in the last case.