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Danger G.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM ) | Plasson R.,Harvard University | Pascal R.,Montpellier University
Chemical Society Reviews | Year: 2012

α-Amino acids are easily accessible through abiotic processes and were likely present before the emergence of life. However, the role they could have played in the process remains uncertain. Chemical pathways that could have brought about features of self-organization in a peptide world are considered in this review and discussed in relation with their possible contribution to the origin of life. An overall scheme is proposed with an emphasis on possibilities that may have led to dynamically stable far from equilibrium states. This analysis defines new lines of investigation towards a better understanding of the contribution of the systems chemistry of amino acids and peptides to the emergence of life. © 2012 The Royal Society of Chemistry.


Allouche A.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM ) | Krstic P.S.,University of Tennessee
Carbon | Year: 2012

The effects of lithium doping of oxidized graphite surfaces on hydrogen adsorption are studied by the first-principles plane-wave density functional theory. Two types of surfaces are considered: a pristine surface and a surface made defective by inclusion of one atomic vacancy. It is shown that oxidization generates epoxide structures that increase the surface reactivity towards lithium as well as towards hydrogen atom retention. This reactivity is compared to a previous using a non-oxidized graphite surface. © 2012 Elsevier Ltd. All rights reserved.


Allouche A.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM ) | Krstic P.S.,Oak Ridge National Laboratory
Carbon | Year: 2012

The effects of lithium doping of pristine and defective graphite surfaces on hydrogen adsorption are studied by the first-principles Plane-Wave Density Functional Theory. The surface defects are simulated by a single atomic vacancy. The DFT calculation is corrected for long-range effects through semi-empirical London terms for each constituent of the system. The lithium doping of the graphite surfaces notably reinforces hydrogen atom binding. Qualitative comparison with experimental results is given using the lithium 1s energy level shifts induced by the atomic vacancy and/or hydrogen trapping. © 2011 Elsevier Ltd. All rights reserved.


Rosato J.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM )
Physical Review Letters | Year: 2011

A kinetic photon transport model that accounts for spatial coherence is applied to line radiation in optically thick plasmas. It is shown that the photon emission and absorption processes are delocalized in space, which alters the global plasma opacity to spectral lines. Based on this analysis, we demonstrate that spectral profiles and escape factors can be much larger than expected from usual formulas. © 2011 American Physical Society.


Allouche A.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM )
Journal of Physical Chemistry C | Year: 2011

This article reports on calculations carried out using the first-principles density functional theory (DFT) on the oxidation process of the beryllium surface and the consequences on hydrogen atom retention. The oxygen molecule adsorption/dissociation reaction is investigated above the special symmetry points (above a surface atom on top and in bridge position, and in the hollow sites of the hexagonal lattice) of the beryllium basal surface. The corresponding energy profiles are built for both the triplet ground state and the singlet first excited state. The structure of the oxidized layer is proposed. A comparison is then given between hydrogen adsorption on partly oxidized beryllium and hydrogen adsorption on beryllium oxide. © 2011 American Chemical Society.


Rosato J.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM )
Transport Theory and Statistical Physics | Year: 2012

The quantum phase space formalism proposed by Wigner is applied to radiation transport problems. It is shown that a generalization of the radiative transfer equation, which accounts for coherence effects, can be obtained within the second quantization formalism. A simplification in the case of stationary medium and slab geometry is considered and applied to low- and high-density plasmas. The obtained results indicate that spectra can be misinterpreted if the light's spatial coherence is neglected. © 2012 Copyright Taylor and Francis Group, LLC.


Allouche A.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM )
Surface Science | Year: 2013

Density functional calculations are here carried out to study the carbon monoxide molecule adsorption on pristine, hydrogenated and hydroxylated beryllium Be (0001) surfaces. The adsorption energies and structures, the activation barriers to molecular adsorption and dissociation are calculated. These reactions are described in terms of potential energy surfaces and electronic density of states. The quantum results are discussed along two directions: the beryllium surface reactivity in the domain of nuclear fusion devices and the possible usage of beryllium as a catalyst of Fischer-Tropsch-type synthesis. © 2012 Elsevier B.V. All rights reserved.


Allouche A.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM )
Journal of Nuclear Materials | Year: 2011

This article reports on calculations carried out using the First Principles density functional theory (DFT) on the oxidization process of the beryllium surface and the consequences on hydrogen atom retention. Detailed analysis of the electron density of states (DOS) provides indications on the oxidized surface reactivity, particularly towards hydrogen (deuterium) adsorption. A comparison is then given between hydrogen adsorption on partly oxidized beryllium and on beryllium oxide. © 2010 Elsevier B.V. All rights reserved.


Allouche A.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM )
Journal of Physics Condensed Matter | Year: 2015

Using the spin-polarized gradient-corrected density functional theory we investigate the adsorption and dissociation of nitrogen molecule and hydrogen nitride radicals on two model surfaces of tungsten, W{1 0 0} and W{1 1 0}. The goal of the investigations is to predict the number and nature of the nitrogenized moieties that could be found on a tungsten surface after nitrogen-seeded hydrogen (deuterium) plasma discharge. The surfaces are considered clean or saturated in hydrogen or nitrogen atoms as they are expected to be after nitrogen seeded hydrogen plasma irradiation. We find that the radicals NH, NH2 and NH3 are dissociated by the catalytic action of the metallic surfaces if they are animated with an initial kinetic energy of less than 2.5 eV. The products of the reaction are a nitrogen atom incorporated into the metal surface and an adsorbed proton. The general conclusion is that nitrogen reduces hydrogen retention on the surface and more generally that the nitrided surfaces should be less reactive than the clean tungsten even if the two surfaces we consider behave quite differently. © 2016 IOP Publishing Ltd.


Allouche A.,CNRS Physics Laboratory Ionic and Molecular Interactions ( PIIM )
Journal of Physical Chemistry C | Year: 2012

This article reports on calculations carried out using first-principles density functional theory (DFT) on beryllium surface hydration. The water adsorption and dissociation reactions are investigated, with a first step considering only water molecules on the pure metal surface. The adsorbed water monolayer structure and the activation energies for dissociation are determined. Then the reactivity of coadsorbed H 2O and O 2 molecules is investigated, and it is shown that water is a very efficient catalyst for oxygen dissociation. The resulting surface structure is strongly perturbed during these processes, and we conclude that this can be considered as the first step of beryllium corrosion. © 2012 American Chemical Society.

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