Francesco Faglioni
California Institute of Technology
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Featured researches published by Francesco Faglioni.
Journal of Physical Chemistry A | 2012
Vyacheslav S. Bryantsev; Francesco Faglioni
Finding suitable solvents remains one of the most elusive challenges in rechargeable, nonaqueous Li-air battery technology. Although ether and amides are identified as stable classes of aprotic solvents against nucleophilic attack by superoxide, many of them are prone to autoxidation under oxygen atmosphere. In this work, we use density functional theory calculations coupled with an implicit solvent model to investigate the autoxidative stability of ether- and N,N-dialkylamide-based solvents. The change in the activation free energy for the C-H bond cleavage by O(2) is consistent with the extent of peroxide production for each class of solvent. Conversely, the thermodynamic stability alone is not sufficient to account for the observed variation in solvent reactivity toward O(2). A detailed understanding of the factors influencing the autoxidative stability provides several strategies for designing molecules with enhanced air/O(2) stability, comparable or superior to that of structurally related hydrocarbons. The mechanism of superoxide-mediated oxidation of hydroperoxides derived from ethers and amides is presented. The degradation mechanism accounts for the primary decomposition products (esters and carboxylates) observed in the Li-air battery with ether-based electrolytes. The identification of solvents having resistance to autoxidation is critical for the development of rechargeable Li-air batteries with long cycle life.
Organic Letters | 2005
Francesco Faglioni; Andrea Ligabue; Stefano Pelloni; Alessandro Soncini; Rosario G. Viglione; Mb Ferraro; Riccardo Zanasi; Paolo Lazzeretti
Traces of magnetizability, traces of magnetic shielding at the hydrogen nuclei, and nucleus-independent chemical shift are not reliable aromaticity quantifiers for planar conjugated hydrocarbons. A measure of aromaticity is provided by the out-of-plane tensor components, whose magnitude is influenced by the pi-ring currents. The failure of nucleus-independent chemical shift in this regard was proved for the molecule shown in the abstract graphic, sustaining a diatropic pi-current. The validity of the ring-current model is reaffirmed. [structure: see text]
International Journal of Quantum Chemistry | 1999
Francesco Faglioni; William A. Goddard
. ABSTRACT: We have developed a version of generalized valence bond GVB that overcomes the major weakness of the perfect pairing approximation without requiring a full transformation of the integrals at each step of the self-consistent orbital optimization. . The method, called generalized valence bond)restricted pairing GVB)RP , describes properly the dissociation of up to triple bonds and provides smooth potential energy surfaces for most chemical reactions. The wave functions obtained are a good starting point for more sophisticated computational techniques. The applicability of the method is illustrated with a few simple examples including multiple-bond dissociations, transition states for symmetry allowed, symmetry forbidden, and radical reactions, as well as reactions at a transition-metal center. The cost of the method compares well with other self-consistent correlated techniques. Q 1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 1)22, 1999
Journal of Physical Chemistry A | 2010
Vyacheslav S. Bryantsev; Mario Blanco; Francesco Faglioni
Knowledge of the precise molecular mechanisms during the discharge and recharge processes in the lithium-air battery is critical for achieving desired improvements in specific capacity, current density, and cyclability. The initial oxygen reduction product formed in the presence of Li(+) ions is lithium superoxide LiO(2). In this study, we report the computed structures and thermodynamic parameters of LiO(2) dimerization in the gas phase, which enables us to provide a baseline for the reaction free energy profile of the subsequent disproportionation of (LiO(2))(2) to lithium peroxide Li(2)O(2) and O(2). Our calculations identified several low-lying (LiO(2))(2) dimers, with the singlet bipyramidal structure giving IR bands that are consistent with the characteristic IR vibration frequencies of (LiO(2))(2) in the oxygen matrix at T = 15-40 K. The activation barrier for (LiO(2))(2) = Li(2)O(2)+O(2) is 10.9 kcal/mol at the UCCSD(T)/CBS level (T = 298 K), suggesting that in the gas phase LiO(2) and its aggregates could only be observed at low temperatures.
Journal of Chemical Physics | 2005
Francesco Faglioni; William A. Goddard
We determined the binding energy of hydrogen to the closest packed surface for all nine group VIII transition metals as a function of surface coverage using quantum mechanics (density functional theory with the generalized gradient approximation) with periodic boundary conditions. The study provides a systematic comparison of the most stable surfaces of the nine group VIII transition metals, leading to results consistent with available surface science studies. We then use these to develop a simple thermodynamic model useful in estimating the surface coverage under typical heterogeneous catalysis conditions and compare these results to temperature programmed desorption experiments.
Origins of Life and Evolution of Biospheres | 2005
Francesco Faglioni; Alessio Passalacqua; Paolo Lazzeretti
A computational algorithm is developed to compute the energy of parity-violation (Epv) due to weak-nuclear forces acting within chain polymers. The method is applied to estimate the magnitude of Epv associated with the folding of α-helices in polypeptide chains and, in turn, of typical proteins. Implications to the development of biological homochirality in nature are discussed in terms of a simple evolutionary model to assess the likelihood for energies of the order of the computed Epv to have determined the direction of natural homochirality.
Chemical Physics Letters | 2003
Stefano Pelloni; Francesco Faglioni; Alessandro Soncini; Andrea Ligabue; Paolo Lazzeretti
Abstract Ab initio current density formalism is used to investigate the response to external magnetic fields of the only known naturally occurring moieties which are formally anti-aromatic, i.e., dithiines. Magnetic susceptibility, nuclear shielding constants, and the topology of induced current densities indicate that although these molecules satisfy Huckel’s rule for being anti-aromatic, they are not. In chiral dithiines, the multipolar expansion of the response contains non-vanishing anapole terms associated with ‘spinning cuff’ current lines.
Rend. Fis. Acc. Lincei | 2013
Stefano Pelloni; Francesco Faglioni; Paolo Lazzeretti
Calculations of nuclear magnetic shielding polarisabilities of cyclic C4H2X2 molecules, for X = O, S, Se and Te, have been carried out. Pseudoscalars of the nuclear magnetic shielding polarisability computed for the heavier nuclei are at least two orders of magnitude larger than those reported so far. Calculations of the rf voltage produced by the rotating chiral electric polarisation, induced by the permanent magnetic dipole moment of 77Se nucleus in 1,2-diselenin and 125Te nucleus in 1,2-ditellurin, are predicted to be ≈40 nV and ≈80 nV, respectively, detectable in principle with a proper experimental set-up. Also the chiral chemical shifts are evaluated and they are found near the experimental detection limit.
Molecular Physics | 2013
Stefano Pelloni; Francesco Faglioni; Paolo Lazzeretti
Parity-violating contributions, with the same magnitude but opposite sign, to the energies of 1,2 enantiomers of dioxin, dithiin, diselenin, ditellurin and dipolonin have been calculated. Theoretical predictions, which can be classified among the largest reported so far, indicate that the P enantiomer is energetically more stable than M. As expected, parity-violating effects increase with the first power of the neutron number and the fourth power of the atomic number for X = O, S, Se, Te and Po. The trend predicted by Laerdahl and Schwerdtfeger [Phys. Rev. A 60, 4439 (1999)] and by Berger [J. Chem. Phys. 129, 154105 (2008)] for H2X2 molecules, characterised by free rotation about the X–X internuclear axis, is therefore confirmed for the series of more rigid C4H4X2 compounds, in which limited deformations can take place.
COMPUTATION IN MODERN SCIENCE AND ENGINEERING: Proceedings of the International Conference on Computational Methods in Science and Engineering 2007 (ICCMSE 2007): VOLUME 2, PARTS A and B | 2008
Béla Barabás; Luciano Caglioti; Francesco Faglioni; Nicola Florini; Paolo Lazzeretti; Marco Maioli; Károly Micskei; Gyula Rábai; Ferdinando Taddei; Claudia Zucchi; Gyula Pályi
The main goal of this communication is to show the utility of empirical approaches combined with mathematical methods in the research regarding the molecular basis of biological chirality. Preparative results (enantiomeric excesses, e.e.) obtained in asymmetric autocatalysis with (AAC) and without (AES) chiral additive were analyzed. Statistical calculations show, that AES (absolute enantioselective synthesis) experiments yield two independent groups of results with prevalence of the R‐ or S‐enantiomer. These are distributed asymmetrically in a second‐order beta distribution. Empirical calculations both on AAC and EAS enable to identify the very low (statistical) e.e.‐s amplified by AES. These initial e.e.‐s show normal distribution. Possible molecular‐level reasons of these results were controlled by quantum chemical MO calculations and compatible mechanism(s) are discussed.