Our main research interest is dedicated to the characterisation of the surfaces of new intermetallic compounds named CMA for “Complex metallic alloy”. Complex Metallic Alloys (CMAs) are defined as intermetallic compounds made of at least two elements with a crystalline structure based on a giant unit cell containing up to some thousands of atoms. CMA structures are best described in terms of their highly symmetric clusters that decorate large to “giant” unit cells and affect the CMA’s physical properties. The chemical decoration and the symmetry of these clusters are similar to those found in quasicrystals, ultimate case of CMAs where the unit cell is infinite (i.e. aperiodic).
One of the main goals is first to optimise the surface preparation of the samples and then to isolate the key parameters responsible for the surface plane selections. Using a combined theoretical (ab initio calculations) and experimental approach, the crystallographic and electronic surface structures of several CMAs have already been determined and atomic models have been proposed. Our studies should provide for instance insight into the stability of the clusters present within the bulk model at the CMA surfaces. It should also answer vital questions on the electronic structure of the topmost surface layers compared to what has been already measured for the bulk of the sample.
Equally, substantial efforts have been put into the use of a CMA surface as templates for adsorption studies. One of the objectives has been the formation of single element monolayers. Such systems of reduced chemical and dimensional complexity should allow us to understand the impact of large to infinite unit cells on the chemical and physical surface properties. In addition, this work should emphasize the role of the cluster-substructure versus the (a)periodicity upon the growth mode of adsorbates.
Throughout these studies, we have identified several preferential nucleation sites on different CMA surfaces using metallic adatoms. Our current research investigates the role of such active sites on the surface reactivity of selected CMA which exhibit important catalytic properties.
Most recent projects involved in :
* Laboratoire International Associé for “Push-Pull AlloyS And Complex CompoundS : from bulk properties to surface functions” LIA PACS2 -France-Slovénie (Directeur partie Française).
* PICS-Investigation of New Complex Alloy Surfaces (INCAS) (2011-2013) France-USA (principal coordinator)
* ANR CAPRICE-Catalytic Properties and surface Reactivity of Intermetallic Compounds (2012-2014)
* COST Action CM0904: Network for Intermetallic Compounds as Catalysts for Steam Reforming of Methanol (IMC-SRM) (2010-2014)
* ANR ASURE-Complex metallic alloys: Surfaces and Reactivity (2009-2011) (principal coordinator)
Recent Publications:“Surfaces of Quasicrystals”J. Ledieu and V. Fournée,Comptes Rendus Physique 15 (2014) 48-57.“Growth and structure of ultrathin alumina films on the (110) surface of γ-Al4Cu9 complex metallic alloy”M. Wardé, J. Ledieu, L. N. Serkovic Loli, M. Herinx, M-C. de Weerd, V. Fournée, S. Le Moal, M-G. Barthés-Labrousse.J. Phys.: Condens. Matter, 26 (2014) 485009.“Quantitative Adsorbate Structure Determination for Quasicrystals Using X-Ray Standing Waves”R. D. Diehl, H. I. Li, S. Y. Su, A. Mayer, N. A. Stanisha, J. Ledieu, K. R. J. Lovelock, Robert G. Jones, A. Deyko, L. H. Wearing, R. McGrath, A. Chaudhuri, and D. P. Woodruff.Phys. Rev. Lett., 113 (2014) 106101.“Self-Organized Molecular Films with Long-Range Quasiperiodic Order”V. Fournée, E. Gaudry, J. Ledieu, M.-C deWeerd, D. Wu and T. LograssoACS Nano 8 (2014) 3646. “Structural Investigation of the (010) surface of the Al13Fe4 catalyst”J. Ledieu, É. Gaudry, L. N. Serkovic Loli, S. Alarcón Villaseca, M.-C. de Weerd, M. Hahne, P. Gille, Y. Grin, J.-M. Dubois and V. Fournée.Phys. Rev. Lett., 110 (2013) 076102.