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We report a combined experimental and theoretical study of the modulation of surface charge transfer on the tetrathiafulvalene (TTF)/Au(111) interface as a function of coverage in the submonolayer regime by combining low-temperature scanning tunneling microscopy, high-resolution photoemission spectroscopy using synchrotron radiation, and density functional theory (DFT) calculations. The modulation is induced by the competition between long-range repulsive Coulombic interactions and short-range attractive hydrogen-bonding interactions. The system shows the characteristic pattern evolution, from monomeric stripes at low coverages to two-dimensional islands, with the formation of labyrinths in the crossover.

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We present a first-principles computational study of the interaction of an H atom with the (010) surface of forsterite (Mg 2 SiO 4 ). Periodic DFT-GGA calculations (PBE) are carried out using the SIESTA code with core pseudopotentials and TZP localized basis sets. Potential energy curves are determined for the approach of the H atom toward different sites of the surface: atop, near, or in between the O, Mg, and Si atoms. An outer adsorption well is found for all investigated sites; it is deepest (162 meV) at a so-called "displaced Mg− O bridge" position. The binding at this well is of the "weak chemisorption"/"strong physisorption" type. An inner stronger chemisorption well (670 meV deep) exists exclusively near an O site but not strictly atop. Depending on the path, we find activation barriers (25− 170 meV high) against chemisorption, the lowest of these occurs for the top O site. General trends of the computed interaction energies qualitatively agree with the QM/MM results of Goumans et al. [Mon. Not. R. Astron. Soc. 2009, 393, 1403, but adsorption binding energies and barrier heights differ significantly.

Using a combination of X-ray photoelectron spectroscopy (XPS) and core level shift first principles calculations, we determine the formation of an unusual intermolecular interaction between porphyrin molecules. We show that protoporphyrin IX molecules (H2PPIX) adsorbed on Cu surfaces at low temperature (LT) form molecular adlayers stabilized by a strong (1.3 eV) tetragonal coordinated H-bond. This unconventional H-bonding involves the four nitrogen atoms in the tetrapyrrole macrocycle of one molecule, four hydrogen atoms, and one of the hydroxyl oxygen atoms from the carboxylic acid groups of an adjacent molecule. The calculations demonstrate that the corresponding fingerprint of this bond is observed in both the nitrogen XPS data, showing a unique peak, and the almost unchanged 1s core level energy of the hydroxyl oxygen atoms. We explain the formation of this bond by a charge rearrangement mechanism that includes proton sharing and migration.

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Este trabajo expone la importancia y singularidad del movimiento de las radios libres en España durante la Transición Española. Se pretende definir qué es una radio libre y cómo fue su evolución y desarrollo desde sus inicios en 1976 hasta 1983 a través de las emisoras más representativas. Metodología. Se han consultado fuentes bibliográficas y hemerográficas (El País, ABC y La Vanguardia), así como documentos y publicaciones vinculadas al movimiento de radios libres. También se han realizado entrevistas a fundadores de emisoras libres históricas. Resultados y conclusiones. Las radios libres fueron un fenómeno comunicativo heterogéneo y paralelo a los medios convencionales: eran participativas, reivindicativas y sin ánimo de lucro, entre otras cualidades. Se ofrece un censo de todas las emisoras que operaron en estos años destacando las iniciativas pioneras de Cataluña, País Vasco, Navarra y Madrid.