Ricardo Gargano

Electron-Lattice Coupling in Armchair Graphene Nanoribbons.

We report the effects of electron-lattice coupling on the charge density distribution study of armchair graphene nanoribbons (GNRs). Here, we perform a theoretical investigation explaining the unexpected electronic density states observed experimentally. By means of a tight-binding approach with electron-lattice coupling, we obtained the same characteristic pattern of charge density along the C-C bonds suggested by both scanning tunneling and transmission electron microscopic measurements. Our results suggest electronic localized states whose sizes are dependent on the GNR width. We also show that our model rescues the quasi-particle charge-transport mechanism in GNRs. The remarkable agreement with experimental evidence allows us to conclude that our model could be, in many aspects, a fundamental tool when it comes to the phenomenological understanding of the charge behavior in this kind of system.

CO2 adsorption on single-walled boron nitride nanotubes containing vacancy defects

The adsorption of a CO2 molecule on the vacancy defect type of armchair (5,5) and zigzag (10,0) single-walled boron nitride nanotubes was studied based on Density Functional Theory (DFT). Vacancy defects were studied and the geometrical modifications implemented on the original hexagonal lattice yielded a considerable level of changes in the electronic properties. These changes are reflected in a greater level of CO2 reactivity in relation to the adsorption over a pristine structure. For all types of studied CO2 molecule interaction, we have found a chemical adsorption process based on binding energy. Furthermore, the CO2 adsorption takes place on the top of the vacancy region. A decomposition state was observed when the CO2 molecule interacted with the armchair nanotube with a vacancy on the nitrogen site. By comparing the values of the adsorption energies with those from other defect approaches present in the literature, we conclude that the proposed protocol presents a possible tool to develop stable and sensible carbon dioxide sensors.

Investigation of the Abstraction and Dissociation Mechanism in the Nitrogen Trifluoride Channels: Combined Post-Hartree–Fock and Transition State Theory Approaches

The present paper concludes our series of kinetics studies on the reactions involved in the complex mechanism of nitrogen trifluoride decomposition. Two other related reactions that, along with this mechanism, take part in an efficient boron nitride growth process are also investigated. We report results concerning two abstraction reactions, namely NF2 + N ⇄ 2NF and NF3 + NF ⇄ 2NF2, and two dissociations, N2F4 ⇄ 2NF2 and N2F3 ⇄ NF2 + NF. State-of-the-art electronic structure calculations at the CCSD(T)/cc-pVTZ level of theory were considered to determine geometries and frequencies of reactants, products, and transition states. Extrapolation of the energies to the complete basis set limit was used to obtain energies of all the species. We applied transition state theory to compute thermal rate constants including Wigner, Eckart, Bell, and deformed theory corrections in order to take tunneling effects into account. The obtained results are in good agreement with the experimental data available in the literature and are expected to provide a better phenomenological understanding of the NF3 decomposition role in the boron nitride growth for a wide range of temperature values.

Rovibrational energies and spectroscopic constants for H2O-Ng complexes.

AbstractIn this work, rovibrational energies and spectroscopic constants for the water −Ng complexes (Ng = He, Ne, Ar, Kr and Xe) were calculated through two different approaches (by solving the Nuclear Schrödinger equation and by applying the Dunham’s method) and using two different potential energy curves (PEC). These PEC were determined using potential parameters obtained through molecular beam scattering experiments and accurate theoretical calculation, respectively. It was found that the theoretical rovibrational energies are in a good agreement (only for the lowest numbers of vibrational states) with those obtained through experimental PEC. Another important conclusions was regarding the calculated first two rovibrational energies for the H 2O−Ar system, that are in a good agreement with the experimental data. Graphical AbstractExperimental potential energy curves for H2O−He, H2O−Ne, H2O−Kr, and H2O−Xe systems and its vibrational states

H2O2–Ng dynamics predictions using an accurate potential energy surface

ABSTRACT Based on ab initio calculations, our research group has built an analytical ground-state potential energy surface (PES) for hydrogen peroxide– noble gas (Ng) interactions, such as H2O2–He, H2O2–Ne, H2O2–Ar, H2O2–Kr, and H2O2–Xe complexes. From this PES, it was verified that the Ng presence does not affect the equilibrium values of the H2O2 dihedral angles. This happens because the H2O2 intramolecular barriers have much higher energies than the atom–bond interaction within these complexes. From this point of view, it is indeed reasonable to consider the H2O2 system as a rigid rotor, frozen at its equilibrium configuration. We present in this work the torsional motion for the H2O2 isolated system, the vibration–rotation energy levels and spectroscopic constants for hydrogen peroxide–noble gas by using the aforementioned PES. The predicted H2O2 torsional motions are in good agreement with both theoretical and experimental results available in the literature. Regarding H2O2–Ng ro-vibrational energies and spectroscopic constants, it is the first time that these calculations are presented in the literature. The current theoretical predictions are expected to be useful in the future experimental investigations.

Previsão de Novos Canais de Reação para o CN + C2H2

Neste trabalho, apresentamos um estudo da reacao do ciano (CN) com a molecula C 2 H 2 . Mais precisamente, determinamos as geometrias, frequencias e energias eletronicas para as diferentes especies envolvidas nos caminhos de reacao do processo CN + C 2 H 2 usando o nivel de calculo M06L/ 6-311++G(d,p). A partir deste estudo, foi possivel propor tres novos caminhos de reacao para este importante processo colisional. DOI: 10.5935/1984-6835.20160038

Predicting New Pathways for the Reaction CN + C2H2

In this work, we present a study of the reaction of cyano (CN) with C2H2 molecule. More precisely, we determined the geometries, frequencies, and electronic energies for the various species involved in the CN+C2H2 reaction pathways at the M06L/6311++G(d,p) level. From this study, it was possible to propose three new pathways for this important reactive scattering process.