Publications

2005

• Plasmon channels in the electronic relaxation of diamond under high-order harmonics femtosecond irradiation.
  
  • Belsky Andrei
  • Esnouf Stéphane
  • Garnov Serguei V.
  • Gaudin Jérôme
  • Geoffroy Ghita
  • Guizard Stéphane
  • Klimentov Serguei M.
  • Martin Patrick
  • Olevano Valério
  • Petite Guillaume
  • Pivovarov Pavel A.
  Laser Physics, MAIK Nauka/Interperiodica, 2005, Letters 2, pp.292-296. We used high order harmonics of a femtosecond titanium-doped sapphire system (pulse duration 25 fs) to realise Ultraviolet Photoelectron Spectroscopy (UPS) measurements on diamond. The UPS spectra were measured for harmonics in the range 13 to 27. We also made ab initio calculations of the electronic lifetime of conduction electrons in the energy range produced in the UPS experiment. Such calculations show that the lifetime suddenly diminishes when the conduction electron energy reaches the plasmon energy, whereas the UPS spectra show evidence in this range of a strong relaxation mechanism with an increased production of low energy secondary electrons. We propose that in this case the electronic relaxation proceeds in two steps : excitation of a plasmon by the high energy electron, the latter decaying into individual electron-hole pairs, as in the case of metals. This process is observed for the first time in an insulator and, on account of its high efficiency, should be introduced in the models of laser breakdown under high intensity. (10.1002/lapl.200510001)
  DOI : 10.1002/lapl.200510001
• Effect of external gamma irradiation on dissolution of the spent UO2 fuel matrix
  
  • Jegou C.
  • Muzeau B.
  • Broudic V.
  • Peuget S.
  • Poulesquen A.
  • Roudil D.
  • Corbel C.
  Journal of Nuclear Materials, Elsevier, 2005, 341, pp.62. Leaching experiments were performed on UO2 pellets doped with alpha-emitters (Pu-238/239) and on spent fuel, in the presence of an external gamma irradiation source (A(60)Co = 260 Ci, D gamma = 650 Gy h(-1)). The effects of alpha, beta, gamma radiation, the fuel chemistry and the nature of the cover gas (aerated or Ar + 4%H-2) on water radiolysis and on oxidizing dissolution of the UO2 matrix are quantified and discussed. For the doped UO2 pellets, the nature of the cover gas clearly has a major role in the effect of gamma radiolysis. The uranium dissolution rate in an aerated medium is 83 mg m(-2) d(-1) compared with only 6 mg m-2 d-1 in Ar + 4%H-2. The rate drop is accompanied by a reduction of about four orders of magnitude in the hydrogen peroxide concentrations in the homogeneous solution. The uranium dissolution rates also underestimate the matrix alteration rate because of major precipitation phenomena at the UO2 pellet surface. The presence of studtite in particular was demonstrated in aerated media; this is consistent with the measured H2O2 concentrations (1.2 x 10(-4) mol L-1). For spent fuel, the presence of fission products (Cs and Sr), matrix alteration tracers, allowed us to determine the alteration rates under external gamma irradiation. The fission product release rates were higher by a factor of 5-10 than those of the actinides (80-90% of the actinides precipitated on the surface of the fragments) and also depended to a large extent on the nature of the cover gas. No significant effect of the fuel chemistry compared with UO2 was observed on uranium dissolution and H2O2 production in the presence of the 6 Co source in aerated conditions. Conversely, in Ar + 4%H-2 the fuel self-irradiation field cannot be disregarded since the H2O2 concentrations drop by only three orders of magnitude compared with UO2
• Use of ion beam analysis techniques to characterise iron corrosion under water radiolysis
  
  • Lapuerta S.
  • Moncoffre N.
  • Millard-Pinard N.
  • Mendes E.
  • Corbel C.
  • Crusset D.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2005, 240, pp.288. The aim of this paper is to study the effect of water radiolysis under 12 MeV proton irradiation on the corrosion behaviour of pure iron. Oxygen and hydrogen playing a crucial role during the corrosion process have been specifically investigated. Heavy desaerated water ( enriched at 99.9% in D) was also used to determine the origin of hydrogen at the iron surface. Proton irradiations were performed at the CERI cyclotron in Orleans. Both sides of the Fe foil (respectively in contact with air and with water) were analysed with ion beam techniques: alpha Rutherford backscattering spectrometry was used to profile oxygen, elastic recoil detection analysis has allowed to profile hydrogen. The use of D2O gives evidence that the hydrogen concentration present on the water face could originate from wet air. In addition, in case of the aerated deionised H2O media, it is shown that the irradiation process induces a strong corrosion. Scanning electron microscopy experiments confirm the formation of oxide precipitates
• Anomalous electron spin resonance behavior of single-walled carbon nanotubes
  
  • Salvetat J.P.
  • Feher T.
  • L'Huillier C.
  • Beuneu François
  • Forro L.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2005, 7207, pp.5440. We have studied the electron spin resonance (ESR) of single-walled carbon nanotubes (SWNTs) both in their pristine state and after irradiation with fast electrons in order to detect the signal of conduction electrons. No metallic Pauli contribution was observed in the global spin susceptibility, the ESR signal of the conduction electrons is undetectable because it is broadened by magnetic impurities. We measured a paramagnetic contribution from localized states, with an effective Curie constant decreasing when the temperature increases, following a deactivation law of the type A-B exp(-E-a/k(B)T). This behavior is supposed to be characteristic of semiconducting SWNTs interacting with metallic impurities from the catalyst
• New high field state of flux line lattice in CeCoIn5
  
  • Kasahara Y.
  • Watanabe T.
  • Izawa K.
  • Sakakibara T.
  • van Der Beek C.J.
  • Hanaguri T.
  • Nohara M.
  • Takagi H.
  • Shishido H.
  • Settai R.
  • Onuki Y.
  • Matsuda Y.
  Physica C: Superconductivity and its Applications, Elsevier, 2005, 426, pp.36-40. We have measured the ultrasound velocity of quasi-two-dimensional superconductor CeCoIn5 with extremely large Pauli paramagnetic susceptibility. The results indicate that the new high field superconducting phase, which is revealed by the recent heat capacity measurements, is characterized by the unusual softening of flux line lattice. The softening is most likely due to the collapse of the flux line lattice tilt modulus and transition to quasi-two-dimensional vortex state. These results provide a strong evidence that the high field phase is the Fulde–Ferrell–Larkin–Ovchinnikov phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicularly to the vortices
• Optical properties of Si and Ge nanocrystals: Parameter-free calculations
  
  • E. Ramos L.
  • Weissker H.-Ch.
  • Furthmüller J.
  • Bechstedt F.
  physica status solidi (b), Wiley, 2005, 242, pp.3053-3063. An overview is given on the electronic and optical properties of Si and Ge nanocrystals. We model freestanding Si and Ge nanocrystals passivated with H, with up to 363 group-IV atoms and 276 H and oxidized nanocrystals with additional silicon oxide shells, e.g. Si41(O60Si42)(O108Si64)H148. The results discussed are based on parameter-free calculations for relaxed atomic structures. The electronic states and the many-body effects are considered within the density-functional theory and the supercell method. Energy gaps are described within the Kohn–Sham independent-particle picture and within the independentquasiparticle picture, whereas electronic excitations are treated within the delta self-consistent method by pair excitation energies. The projector-augmented wave method allows the calculation of optical matrix elements, oscillator strengths, optical spectra, and radiative lifetimes. We discuss quantum confinement, structural relaxation, oxidation, and the role of defects in oxidized Si NCs.
• Photoconductivité et photoémission de diamant(s) sous irradiation XUV femtoseconde
  
  • Petite Guillaume
  • Gaudin Jérôme
  • Geoffroy Ghita
  • Guizard Stéphane
  • Esnouf Stéphane
  • Olevano Valério
  • Klimentov Serguei M.
  • Pivovarov Pavel A.
  • Garnov Serguei V.
  • Carre Bertrand
  • Martin Patrick
  • Belsky Andrei
  Journal de Physique IV Proceedings, EDP Sciences, 2005, 127, pp.219. We report à study of the photoconductivity (PC) induced in different types of diamonds (type IIa single crystals and CVD) by femtosecond XUV pulses (high order harmonics - up to 19th - of a titanium doped laser). We also reprot UPS spectras obtained with harmonics 13 to 29. Depending on the harmonic's order, the PC signal first increases (orders 9 to 13) and then decreases. If the increase is easily interpreted as resulting from a carrier multiplication process, the further decrease has not yet received an explanation. The UPS measurements also suggest a strong effect of the plasmon relaxation on the carrier multiplication process. Finally, we performed a preliminary GW ab-initio calculation of the carriers lifetime, acounting for electron-electron interactions. In the near-bandgap region, it behaves approximatively according to the Fermi-liquid model, from which it strongly departs at higher energies, which is attributed to band-structure effects and to plasmon excitations.
• Ferromagnetic domain structure of La0.78Ca0.22MnO3 single crystals
  
  • Jung G.
  • Markovich V.
  • van Der Beek C.J.
  • Mogilyansky D.
  • Mukovskii M.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2005, 72 (134412), pp.1-6. The magneto-optical technique has been employed to observe spontaneous ferromagnetic domain structures in La0.78Ca0.22MnO3 single crystals. The magnetic domain topology was found to be correlated with the intrinsic twin structure of the investigated crystals. With decreasing temperature the regular network of ferromagnetic domains undergoes significant changes resulting in apparent rotation of the domain walls in the temperature range of 70–150 K. The apparent rotation of the domain walls can be understood in terms of the Jahn-Teller deformation of the orthorhombic unit cell, accompanied by additional twinning.
• Comment on "Sound Modes broadening in Quasicrystals
  
  • Coddens Gerrit
  , 2005. Recently de Boissieu et al. proposed an explanation for the broadening of acoustic modes observed in quasicrystals (QC). It is the transcription of a well-known model used for glasses. We raise two fundamental objections against applying it to QC.
• Effect of alpha irradiation on UO2 surface reactivity in aqueous media
  
  • Jegou C.
  • Muzeau B.
  • Broudic V.
  • Poulesquen A.
  • Roudil D.
  • Jorion F.
  • Corbel C.
  Radiochimica Acta, Oldenbourg Wissenschaftsverlag, 2005, 93, pp.35. The option of direct disposal of spent nuclear fuel in a deep geological formation raises the need to investigate the long-term behavior of the UO2 matrix in aqueous media subjected to alpha-beta-gamma radiation. The beta-gamma emitters account for most of the activity of spent fuel at the moment it is removed from the reactor, but diminish within a millennial time frame by over three orders of magnitude to less than the long-term activity. The latter persists over much longer time periods and must therefore be taken into account over a geological disposal time scale. Leaching experiments with solution renewal were carried out on UO2 pellets doped with alpha emitters (Pu-238 and Pu-239) to quantify the impact of alpha irradiation on UO2 matrix alteration. Three batches of doped UO2 pellets with different alpha flux levels (3.30 x 10(4), 3.30 x 10(5), and 3.2 x 10(6) alphacm(-2) s(-1)) were studied. The results obtained in aerated and deaerated media immediately after sample annealing or interim storage in air provide a better understanding of the UO2 matrix alteration mechanisms under alpha irradiation. Interim storage in air Of UO2 pellets doped with alpha emitters results in variations of the UO2 surface reactivity, which depends on the alpha particle flux at the interface and on the interim storage duration. The variation in the surface reactivity and the greater uranium release following interim storage cannot be attributed to the effect of alpha radiolysis in aerated media since the uranium release tends toward the same value after several leaching cycles for the doped UO2 pellet batches and spent fuel. Oxygen diffusion enhanced by alpha irradiation of the extreme surface layer and/or radiolysis of the air could account for the oxidation of the surface UO2 to UO2+x. However, leaching experiments performed in deaerated media after annealing the samples and preleaching the surface suggest that alpha radiolysis does indeed affect the dissolution, which varies with the flux at the UO2/water interface
• Mécanismes fondamentaux de l'ablation laser femtoseconde en "flux intermédiaire
  
  • Petite Guillaume
  , 2005, pp.319. This chapter aims at identifying what is specific to femtosecond laser ablation. It reviews the essential basic processes which contribute to femtosecond laser ablation of various materials : energy absorption by the material's electrons, electronic relaxation processes involving either electron-electron or electron-lattice interactions. A number of widely used models are briefly discussed, as well as some pending questions.
• Spin-induced forbidden evanescent states in III-V semiconductors
  
  • Rougemaille N.
  • Drouhin H.J.
  • Richard S.
  • Fishman G.
  • Schmid A.K.
  Physical Review Letters, American Physical Society, 2005, 9518, pp.6406. Within the band gap of a semiconductor no electronic propagating states are allowed, but there exist evanescent states which govern charge transport such as tunneling. In this Letter, we address the issue of their spin dependence in III-V semiconductors. Taking into account the spin-orbit interaction, we treat the problem using a k center dot p 14x14 Hamiltonian that we numerically compute for GaAs. Our results show that the removed spin degeneracy in the band gap can lead to giant energy splittings and induces forbidden zones in k space where evanescent states are suppressed
• Alfred Wilm et les débuts du Duralumin
  
  • Hardouin-Duparc O.
  Cahiers de l'histoire de l'aluminium, 2005, 34, pp.62-76. Loin d'être la découverte " romantique " parfois décrite, la mise au point du Duralumin se fit de façon volontariste, au début du siècle, dans un contexte militaro-industriel. L'invention d'un alliage conservant les qualités de légèreté de l'aluminium, mais lui adjoignant la dureté nécessaire à la production d'armes, fut obtenue par l'ingénieur Wilm dans le cadre d'un laboratoire militaire prussien. Le Duralumin – baptisé par jeu de mots – s'imposa d'autant plus rapidement aux autres pays industrialisés que ceux-ci menaient en parallèle des recherches similaires (ce qui entraina d'ailleurs des rivalités autour de la paternité du matériau). L'ensemble de ces recherches contribua à la compréhension progressive des mécanismes fondamentaux du durcissement des alliages par maturation
• Strong light-matter coupling at room temperature in simple geometry GaN microcavities grown on silicon.
  
  • Semond F.
  • Sellers I.R.
  • Natali F.
  • Byrne D.
  • Leroux M.
  • Massies J.
  • Ollier N.
  • Leymarie Joël
  Applied Physics Letters, American Institute of Physics, 2005, pp.3.
• Energy dependence of the exchange-correlation kernel of time-dependent density functional theory: A simple model for solids
  
  • Botti Silvana
  • Fourreau A.
  • Nguyen F.
  • Renault Y.-O.
  • Sottile F.
  • Reining L.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2005, 72, pp.125203. Time-dependent density functional theory faces an important problem when it comes to extended systems: The long-range component of the exchange-correlation kernel fxc is completely absent from local density or generalized gradient approximations, but it is believed to be present in the “exact” fxc . Several attempts have been made to solve this issue, the simplest of them being the use of a model static long-range kernel of the form −αstatic∕q2 . In this paper, we propose and motivate a dynamical extension of this model of the form −(α+βω2)∕q2 . The dynamical model is then used to calculate the dielectric function of a large variety of semiconductors and insulators. The absorption spectra of large gap insulators are remarkably improved with respect to calculations where the kernel is taken to be static. This approach is valid also for energies in the range of plasmons, and hence it yields, e.g., good electron energy loss spectra. Finally, we present some simple theoretical arguments that relate the parameters of the model to physical quantities, like the dielectric constant and the plasmon frequency. (10.1103/PhysRevB.72.125203)
  DOI : 10.1103/PhysRevB.72.125203
• Magnetic structure of beta-ErD2: Long-range and short-range order from powder neutron diffraction
  
  • Vajda P.
  • André G.
  • Udovic T.J.
  • Erwin R.W.
  • Huang Q. S.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2005, 71, pp.054419. Two parallel neutron powder diffraction investigations were performed on different specimens of ErD2 at the LLB (CEN Saclay) and at NIST for the determination of its magnetic structure. It comprises, below Tn=2.23 K, two coexisting sinusoidally modulated antiferromagnetic (AF) configurations, M' and M'', with the respective incommensurate propagation vectors, k'=(0.275,0.275,0.750), together with its third harmonic 3k', and k''=(0.120,0.120,0.750). Contrary to other heavy rare-earth dideuterides, no commensurate AF configuration could be detected down to 120 mK. On the other hand, similar to earlier observations on HoD2 and TbD2, magnetic short range order (SRO shows up near 1.5 K in ErD2 after the disappearance of certain M'' lines. This SRO seems to correlate with the hexagonal gamma-phase of the trideuterite and suggests an electronic phase separation with memory effects
• Multiple superconducting phases in heavy fermion superconductors
  
  • Matsuda Y.
  • Izawa K.
  • Watanabe T.
  • Kasahara Y.
  • Nakajima Y.
  • Sakakibara T.
  • van Der Beek C.J.
  • Nohara M.
  • Hanaguri T.
  • Takagi H.
  • Goryo J.
  • Maki K.
  • Thalmeier P.
  • Osaki S.
  • Sugawara H.
  • Sato H.
  • Shishido H.
  • Settai R.
  • Onuki Y.
  Journal of Physics and Chemistry of Solids, Elsevier, 2005, 66, pp.1365. We show that in recently discovered heavy fermion superconductors, quasi two-dimensional CeCoIn5 and skutterudite PrOs4Sb12, multiple superconducting phases with different symmetries manifest themselves below T-c. The ultrasound velocity measurements revealed that in CeCoIn5 the Fulde-Ferrel-Larkin-Ovchinikov phase, in which the order parameter is spatially modulated and has planar nodes aligned perpendicular to the vortices, appears at low temperature and high field. The angle resolved magnetothermal transport measurements revealed that in PrOs4Sb12 a novel change in the symmetry of the superconducting gap function occurs deep inside the superconducting state. These results open up a new realm for the study of the superconductivity with multiple phases
• Raman and EPR studies of ß-irradiated oxide glasses: The effect of iron concentration
  
  • Olivier F.Y.
  • Boizot B.
  • Ghaleb D.
  • Petite G.
  Journal of Non-Crystalline Solids, Elsevier, 2005, 351, pp.1061. The study of iron concentration on the oxide glass structure has shown evidence of depolymerization of the vitreous network with increasing iron content and especially with Fe2+ amount for all types of glass. For all glass compositions studied, we observe by EPR a blockage of defects creation processes under beta irradiation for glasses doped with more than 1 wt% of Fe2O3. Reduction processes of Fe3+ under irradiation is also detected. Moreover for sodalime glass samples, beta irradiation induces depolymerization, in opposite of what was expected and observed for other glasses. Anyway, adding iron up to 4 wt% Fe2O3 always diminishes the beta irradiation effects. This has been linked to the observed iron reduction and to the ability of iron, maybe coupled with charge trapping processes to consume excitons
• Conductance in multiwall carbon nanotubes and semiconductor nanowires
  
  • Dayen J.F.
  • Wade T.L.
  • Konczykowski M.
  • Wegrowe J.E.
  • Hoffer X.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2005, 7207, pp.3402. Electronic transport in an ensemble of multiwall carbon nanotubes and semiconductor nanowires was compared. The nanotubes and nanowires are obtained by template synthesis and are contacted in a current perpendicular to the plane geometry by using different methods. In all cases, the nonohmic behavior of the conductance, the so-called zero-bias anomaly, shows a temperature dependence that scales with the voltage dependence. This robust scaling law describes the conductance G(V,T) by a single coefficient alpha. A universal behavior as a function of alpha is found for all samples. Magnetoconductance measurements furthermore show that the conduction regime is weak localization. The observed behavior can be understood in terms of the Coulomb blockade theory, providing that a single tunnel barrier is present. This hypothetical tunnel barrier would have a resistance of the order of 2500 Omega and a typical energy of about 40 meV for all samples
• Growth dynamics of hydrogenated silicon nanoparticles under realistic conditions of a plasma reactor
  
  • Vach H.
  • Brulin Q.
  • Chaâbane N.
  • Novikova T.
  • Roca I Cabarrocas Pere
  • Kalache B.
  • Hassouni K.
  • Botti Silvana
  • Reining Lucia
  Computational Materials Science, Elsevier, 2005, 35, pp.216-222. We present results of an extensive numerical study that was motivated by the experimental problem to understand under which conditions SinHm nanoparticles deposited by plasma enhanced chemical vapor deposition (PECVD) take an amorphous or a crystalline structure. A crystalline structure of those particles is crucial, for example, for the electrical properties and lifetime of polymorphous solar cells. First, we use a fluid dynamics model to characterize the experimentally employed silane plasma. The resulting relative densities for all plasma radicals, their temperatures, and their collision interval times are then used as input data for detailed semiempirical quantum molecular dynamics simulations. As a result the growth dynamics of nanometric hydrogenated silicon SinHm clusters is simulated starting out from the collision of individual SiHx radicals under the plasma conditions derived above. We demonstrate how the details of the plasma determine the amorphous or crystalline character of the forming nanoparticles. Finally, we show a preliminary absorption spectrum based on ab initio time-dependent DFT calculations for a crystalline Si10H16 cluster to demonstrate the possibility to monitor the cluster growth in situ. (10.1016/j.commatsci.2004.07.010)
  DOI : 10.1016/j.commatsci.2004.07.010
• Nucleation and growth of single wall carbon nanotubes
  
  • Beuneu Francois
  Solid State Communications, Elsevier, 2005, 136, pp.462. The nucleation and growth of single wall carbon nanotubes from a carbon-saturated catalytic particle surrounded by a single sheet of graphene is described qualitatively by using a very restricted number of elementary processes, namely Stone-Wales defects and carbon bi-interstitials. Energies of the different configurations are estimated by using a Tersoff energy minimization scheme. Such a description is compatible with a broad variety of size or helicity of the tubes. Several mechanisms of growth of the embryos are considered: one of them is made more favourable when the tubes embryos are arranged in an hexagonal network in the graphene plane. All the proposed mechanisms can be indefinitely repeated for the growth of the nanotubes. (10.1016/j.ssc.2005.09.007)
  DOI : 10.1016/j.ssc.2005.09.007
• Photoconductivité et photoémission de diamant(s) sous irradiation XUV femtoseconde
  
  • Gaudin J.
  • Geoffroy G.
  • Guizard S.
  • Esnouf S.
  • Olevano Valério
  • Petite G.
  • Klimentov S.M.
  • Pivovarov P.A.
  • Garnov S.V.
  • Carre B.
  • Martin P.
  • Belsky A.
  Journal de Physique IV Proceedings, EDP Sciences, 2005, 127, pp.131-138. En fonction de l'ordre de l'harmonique, on constate que le signal de PC augmente tout d'abord (harmoniques 9 à 13) puis diminue au delà. Si l'augmentation s'interprète aisément comme résultant de phénomènes de multiplication par collisions inélastiques, la diminution ultérieure n'a pas pour le moment d'explication. Les mesures de spectre de photoémission suggèrent un effet important de la relaxation par émission de plasmons. Enfin, nous avons réalisé le premier calcul ab-initio de la durée de vie des porteurs tenant compte des interactions électron-électron, à l'aide d'une approche de théorie quantique à plusieurs corps de type GW. Au voisinage du gap, on observe un comportement proche de celui d'un liquide de Fermi. A plus haute énergie on observe des déviations à ce comportement, provenant d'effets de structure de bande d'une part, et d'excitations de plasmons d'autre part
• Relationship between structure, segregation and electrical activity in grain boundaries
  
  • Lamzatouar A.
  • Palais Olivier
  • B. M. Hardouin Duparc O.
  • Thibault J.
  • Charaï A.
  Journal of Materials Science, Springer Verlag, 2005, 40, pp.3163-3167. Using the contactless microwave phase-shift technique (μ W-PS) and High Resolution Transmission Electron Microscopy (HRTEM), we show that the twist and mixed parts of a < 110 > Σ = 51(θ = 16.10∘) grain boundary in germanium (Ge) are electrically active. We also show that we can passivate the electrically active grain boundaries by sulfur segregation which has been studied by energy filtering HRTEM. Atomistic simulations show that the most favorable places for this segregation are the high energy sites of grain boundary
• Deuterium trapping in sintered polished UO2 disks
  
  • Labrim H.
  • Barthe M.F.
  • Sauvage T.
  • Desgardin P.
  • Blondiaux G.
  • Corbel C.
  • Miserque F.
  • Piron J.P.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2005, 240, pp.434. In this work we present deuterium analysis performed using the H-2(He-3, alpha)H-1 Nuclear Reaction Analysis method. Different sets of sintered polished uranium oxide disks have been investigated before and after annealing at 400 degrees C in ArD2 atmosphere. Heterogeneous lateral deuterium distributions have been found for all the ArD2 annealed UO2 disks. The average deuterium amount increases after annealing at 400 degrees C in ArD2 and decreases after a second annealing at 400 degrees C in vacuum whatever is the set of sintered polished uranium oxide disks
• Many-body perturbation theory using the density-functional concept: beyond the GW approximation
  
  • Bruneval Fabien
  • Sottile Francesco
  • Olevano Valério
  • del Sole Rodolfo
  • Reining Lucia
  Physical Review Letters, American Physical Society, 2005, 94, pp.186402. We propose an alternative formulation of Many-Body Perturbation Theory that uses the densityfunctional concept. Instead of the usual four-point integral equation for the polarizability, we obtain a two-point one, that leads to excellent optical absorption and energy loss spectra. The corresponding three-point vertex function and self-energy are then simply calculated via an integration, for any level of approximation. Moreover, we show the direct impact of this formulation on the timedependent density-functional theory. Numerical results for the band gap of bulk silicon and solid argon illustrate corrections beyond the GW approximation for the self-energy.