CINaM - Centre Interdisciplinaire de Nanoscience de Marseille


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A venir ...

Jeudi 27 Septembre 2018
Lutz Hammer
Solid State Physics, Friedrich-Alexander University Erlangen-Nuremberg, Germany
Monatomic Transition-Metal-Oxide Chains Grown on Ir and Pt: A New Class of Hybrid Material
In modern heterogeneous catalysis, metal-oxide composite materials, i.e. combinations of transition metal oxides (TMOs) and noble-metals at the nanometer scale, are known to exhibit extraordinary performance for a variety of low temperature catalytic oxidation reactions such as e.g. carbon monoxide conversion. A detailed characterization of the metal/oxide interfaces on the atomic level, however, is rarely possible due to the inaccessibility of nanoparticles for standard surface science techniques. For that model systems grown under well-defined conditions on single crystal surfaces have to be studied. When sub-monolayer amounts of 3d transition metals (TM = Mn, Fe, Co, Ni) being either deposited on (or dissolved in) Ir(100) or Pt(100) surfaces are annealed in oxygen they form a dense and highly ordered array of TMO2 chains with a monatomic metal core [1]. The oxide chains can be completely reduced under H2 or CO flux leading to a 2-dimensionally ordered Ir2TM or Pt2TM surface alloy, respectively [2]. Conversely, for some systems the oxide wires can also be further oxidized towards TMO3 chains even under UHV conditions using strong oxidants such as NO2 [2]. The chemical and structural transitions are fully reversible so that the systems can be switched back and forth using the respective agents O2, NO2 and H2. Thus, these highly ordered structures might serve as ideal model systems to study various redox reactions at metal-oxide hybrid catalysts with crystallographic precision. The presentation focuses on the growth, geometrical structure, energetics and reactivity of these systems investigated experimentally by quantitative LEED-IV analyses, STM, TPD, and XPS, as well as theoretically by DFT. [1] P. Ferstl et al., Phys. Rev. Lett. 117 (2016) 046101 [2] P. Ferstl et al., Phys. Rev. B 96 (2017) 085407

Jeudi 04 Octobre 2018
Boris Le Guennic
nstitut des Sciences Chimiques de Rennes, UMR CNRS 6226 Université de Rennes 1, 263 Av. du Général Leclerc, 35042 Cedex Rennes, France
Ab initio calculations of lanthanide complexes: from single molecule magnets to circularly polarized luminescence
Complexes containing trivalent lanthanide ions are of great interest in numerous fields due to their specific spectroscopic and magnetic characteristics. In particular, they can give rise to single molecule magnets (SMM) with slow magnetic relaxation, uniaxial magnetic anisotropy and high-energy barrier to the reversal of the magnetic moment. These features originate from the subtle interplay between the spin-orbit coupling and the crystal field interaction created by the ligands surrounding the lanthanide ion. Few general rules for building SMM have been formulated to date but no fundamental magneto-structural relationship explaining the behavior of lanthanide-based SMM has been proposed yet. To this end, and in addition to experimental evidences (SQUID magnetometry, EPR spectroscopy, polarized neutron diffraction...) ab initio calculations (SA-CASSCF/PT2/SI- SO) are one of the most appropriate theoretical tools to get reliable insights into the electronic structure of these compounds. Herein, the recent elucidation of the magnetic behavior of several lanthanide-based complexes is reported.[1] The limits of this computational approach is discussed. Finally, recent advances in the calculations of circularly polarized luminescence (CPL) and paramagnetic NMR (pNMR) in lanthanide complexes are also presented. [1] a) T. T. da Cunha, J. Jung, M.-E. Boulon, G. Campo, F. Pointillart, C. L. M. Pereira, B. Le Guennic, O. Cador, K. Bernot, F. Pineider, S. Golhen, L. Ouahab J. Am. Chem. Soc. 2013, 135, 16332. b) F. Pointillart, B. Le Guennic, O. Cador, O. Maury, L. Ouahab, Acc. Chem. Res., 2015, 48, 2834. c) J.-K. Ou-Yang, N. Saleh, G. Fernandez Garcia, L. Norel, F. Pointillart, T. Guizouarn, O. Cador, F. Totti, L. Ouahab, J. Crassous, B. Le Guennic Chem. Commun. 2016, 52, 14474. d) F. Pointillart, O. Cador, B. Le Guennic, L. Ouahab Coord. Chem. Rev. 2017, 346, 150. e) M. Xémard, A. Jaoul, M. Cordier, F. Molton, O. Cador, B. Le Guennic, C. Duboc, O. Maury, C. Clavaguéra, G. Nocton Angew. Chem. Int. Ed. 2017, 56, 4266. f) L. Norel, L. E. Darago, B. Le Guennic, K. Chakarawet, M. I. Gonzalez, J. H. Olshansky, S. Rigaut, J. R. Long Angew. Chem. Int. Ed. 2018, 57, 1933.

Mardi 13 Novembre 2018
Ping Yang
Theoretical Division, Los Alamos National Laboratory Los Alamos, NM, 87545
Predictive Modeling of Actinide Chemistry and Nanomaterials
Nuclear energy represents a critical tool to ensure sustainable energy supplies and curb greenhouse gases. However, the development of nuclear energy is still hampered by safety concerns associated with handling and processing of spent fuel and high-level waste. The complicated electronic structure of actinide complexes leads to their versatility of chemical bonding, reactivity, and spectral and magnetic properties. Advances in high-performance computing and quantum chemistry have greatly accelerated the understanding of complex systems related to heavy elements including both molecules and nanomaterials. In this talk, I will present recent progress on the understanding of 5f-orbital participation in chemical bonding across the actinide series of molecular systems that are important for separation and the understanding of interfacial chemistry in controlling the morphology of f-element nanomaterials.