Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: The extraordinary success of graphene and its tremendous potential applications [1] paved the way for the rising of a completely new family of two dimensional materials. [2] Graphene is a semimetal with zero-gap, which limits its use in the electronics technology. Transition metal dichalcogenides present a band gap in the range of 1.5 -2.5 eV [3] (depending on the thickness, strain level and chemical composition), which makes them inappropriate for some optoelectronics applications where band gaps in the 0.1 -1 eV range are commonly preferred. [4] Black phosphorous (BP), [5] a layered allotrope of phosphorous, presents an energy gap in this range and hence it is now intensely studied to better understand its electronics properties in the few-layer conformation. However, it shows a relatively large reactivity. Exfoliated flakes of BP are highly hygroscopic and tend to uptake moisture from

International audienceWe present a combined experimental and theoretical study of the complex dynamics of excited doubly ionized glycine molecules in the gas phase. Multicoincidence mass spectroscopic techniques together with ab initio molecular dynamics simulations and density functional theory calculations allow us to show that an ultrafast intramolecular hydrogen migration (∼30 fs) appears in competiton with the expected Coulomb repulsion

We present a combined experimental and theoretical study of fragmentation of small Cn clusters (n = 5,7,9) produced in charge transfer collisions of fast (nu = 2.6 a.u.) singly charged Cn+ clusters with He. Branching ratios for all possible fragmentation channels have been measured. Comparison with microcanonical Metropolis Monte Carlo simulations based on quantum chemistry calculations allows us to determine the energy distribution of the excited clusters just after the collision.

We present a statistical fragmentation study of the C 5 , C 7 , and C 9 carbon clusters using the Metropolis Monte Carlo and Weisskopf methods. We show that inclusion of several isomeric forms as well as rotational effects is essential to reproduce the experimental observations. We have found that, for cluster excitation energies around 10 eV, several fragmentation channels are efficiently populated, but the dominant one always corresponds to C n−3 /C 3 . For high enough excitation energies, we observe first-order phase transitions corresponding to a complete breakup of the cluster.

Fullerene anions and cations have unique structural, electronic, magnetic and chemical properties that make them substantially different from neutral fullerenes. Although much theoretical effort has been devoted to characterizing and predicting their properties, this has been limited to a fraction of isomeric forms, mostly for fullerene anions, and has practically ignored fullerene cations. Here we show that the concepts of cage connectivity and frontier π orbitals allow one to understand the relative stability of charged fullerene isomers without performing elaborate quantum chemistry calculations. The latter is not a trivial matter, as the number of possible isomers for a medium-sized fullerene is many more than 100,000. The model correctly predicts the structures observed experimentally and explains why the isolated pentagon rule is often violated for fullerene anions, but the opposite is found for fullerene cations. These predictions are relevant in fields as diverse as astrophysics, electrochemistry and supramolecular chemistry.

We have studied the structure of small doubly charged carbon clusters using density functional (DFT) and coupled-cluster (CC) theories. We have found that, with the exception of C4 2+ and C7 2+, the most stable geometry corresponds to linear structures of D ∞ h symmetry. This is at variance with the behavior observed in neutral and singly charged carbon clusters. We have also evaluated dissociation energies corresponding to various dissociation channels that are useful in mass spectrometry experiments. This requires that absolute energies of neutral and singly charged species are evaluated at the same level of theory. As a byproduct of the latter calculations, we have evaluated first and second ionization potentials that are still unavailable in the literature. Harmonic frequencies for the doubly charged species have been also evaluated.

A detailed experimental and theoretical investigation of the dynamics leading to fragmentation of doubly ionized molecular thiophene is presented. Dissociation of double-ionized molecules was induced by S 2p core photoionization and the ionic fragments were detected in coincidence with Auger electrons from the core-hole decay. Rich molecular dynamics was observed in electron-ion-ion coincidence maps exhibiting ring breaks accompanied by hydrogen losses and/or migration. The probabilities of various dissociation channels were seen to be very sensitive to the internal energy of the molecule. Theoretical simulations were performed by using the semiempirical self-consistent charge-density-functional tight-binding method. By running thousands of these simulations, the initial conditions encountered in the experiment were properly taken into account, including the systematic dependencies on the internal (thermal) energy. This systematic approach, not affordable with first-principle methods, provides a good overall description of the complex molecular dynamics observed in the experiment and shows good promise for applicability to larger molecules or clusters, thus opening the door to systematic investigations of complex dynamical processes occurring in radiation damage.

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