My Lab : Institut Lumière Matière  
Our High Pressure Platform

• How extreme pressure conditions or mechanical sollicitations may allow to modify the geometry, topology or dimension of nanomaterials?
• How going nano modifies the response to extreme conditions as phase diagram, mechanical properties or physical properties in general?
• Which opportunities to develop novel nanomaterials using extreme conditions?

Carbon sp² allotropes such as graphite, graphene or nanotubes are very interesting in this regard. In these systems, characterized by the most cohesive extended chemical bond, the topological or the dimensional constraints are key elements to define their physical properties. I have been carrying out experiments to tune these constraints through pressure and temperature thermodynamic parameters. The studies cover multiple scales expanding from the structural evolution at the atomic scale to macroscopic evolutions as in surface adhesion and going through nanoscale changes as the carbon nanotube radial deformation or mesoscale studies (porosity under high pressure). In order to precisely quantify the different evolutions, we need to combine original experimental approaches with advanced modeling.

Presently ongoing projects

• Graphene origami. The physics of folding of 2D materials and their technological use.
• High pressure in 2D materials. In physics, pressure and low-dimensionality appear as contradictory terms. Combining them constitutes a formidable challange for the physics of condensed matter and opens new horizons for material research.

Some recent highlights:

• The best high pressure phase diagram of carbon nanotubes. Combining experiments and modelling, and after years of work to understand all the physical mechanisms into play, we have given the evolution of the collapse pressure in carbon nanotubes as a function of the diameter and the number of nanotube walls.

Publication: "Collapse phase diagram of carbon nanotubes with arbitrary number of walls. Collapse modes and macroscopic analog", Y. Magnin, F. Rondepierre, W. Cui, D. Dunstan and A. San-Miguel, Carbon, 178, 552-562 (2021)  (Arxiv version)...

• The first high pressure transformation in diatomic molecules. Diatomic molecules are ubiquitous in our environment, as in the air we breathe, but if we increase the pressure by gradually bringing them closer together, until when can we still speak of differentiated molecules? Modelling and measuring with an accuracy close to a thousandth of an Angstrom the change with pressure of the intramolecular distance of the halogens (I₂, Br₂), we have shown the formation of bonds between molecules which affect the state of the molecule itself at pressures much lower than the metallisation or dissociation pressures of diatomic molecules. This phenomenon could be more general and have implications in areas such as the structure of giant planets, composed essentially of another diatomic molecule at high pressure: hydrogen.

Publication : "Halogen molecular modifications at high pressure: the case of iodine" Journal Physical Chemistry Chemical Physics, 23 (5), 3321-3326 (2021). This paper was selected as "Hot topic 2021" by the editor and is distributed free of charge.

Scientific career synopsis

The study of condensed matter under extreme conditions of pressure has guided my research activity. First, for about 10 years in the study of simple semiconductors (GaN, ZnTe, ZnSe, HgTe, GaSe, GaS, GaTe) through their phase diagram, equations of state and structural evolution. Then, after a PhD thesis supervision on the structure of liquids under high pressure, I started in 1999 a new research activity on the study of nanomaterials and nanosystems (clathrates, fullerites, nanotubes or graphene) under extreme conditions of pressure and temperature. I founded a research group on this activity and created an adapted experimental platform in collaboration with geologist from the ENS Lyon. To further enhance my research activities, I have contributed to the development of adapted tools for the experimental study of condensed matter under extreme conditions of pressure and temperature, either using large facilities (synchrotrons or neutron reactors) or for laboratory experiments.

Timeline

1989. B.Sc. University of Barcelona, Spain
1993. Ph.D. University Pierre Marie Curie, Paris, France
1993 - 1997. Scientist position at the European Synchrotron Radiation Facility ( Grenoble, France)
1997-2003. Maître de Conférences, University Lyon I, France
Since 2003. Professor, University Lyon I, France.
2010. Deputy Director of Laboratoire de Physique de la Matière Condensée et Nanostructures, UMR CNRS 5586, University Lyon 1.
2011-2012. Director of Laboratoire de Physique de la Matière Condensée et Nanostructures, UMR CNRS 5586, University Lyon 1.
2013-2014. Deputy director of Institut Lumière Matière, UMR CNRS 5306, University Lyon-1
2015-2020. Director of Fédération de Physique Andrée-Marie Ampère,  FR3127 CNRS/UCBL/ENSL/ECL/INSA Lyon
2020. President of the Rhône section of the French Physical Society
2021. President of the Society of Friends of André-Marie Ampère which runs the Ampère's Museum.