Research themes

1.    Structure and dynamics of simple molecular solids

The study of molecular solids is a ‘building block’ of the team research activity with high visibility. Our interests span several systems, each presenting specific scientific questions. Our current projects concern: polymorphism in solid CO₂, in particular with regards to polymeric phases; “salty” ice (ice doped with salts such as LiCl, NaCl, MgCl2, LiBr) and ice isostructural compounds, such as NH4F, NH4HF2 and mixed NH4F-ice compounds; magnetism and spin-libron coupling in solid oxygen and oxygen-nitrogen alloys.

2.    Properties of clathrate and mixed ices

Water, ammonia, methane, and hydrogen are largely present in nature, both in planetary crusts and in giant planets interiors, where they experience a very broad range of P-T conditions. Most studies have been so far devoted to characterize the properties of pure systems while they mix in nature. We have several ongoing projects to study the structural, dynamical and conductivity properties of binary mixtures and compounds of H2O, CH4, NH3 and H2 under disparate P-T conditions relevant either for energy storage, environmental or planetary studies. These projects have been awarded several fundings from Labex MATISSE, ANR, ILL, FNS, China Scholarship Council.

3.    Melting and simple liquids

Studies of simple liquids are fundamental in the development of our understanding of this state of matter, for their simple atomic and electronic structures make them more amenable to theoretical description at the microscopic level. In particular, they are considered benchmark systems for ab initio theoretical methods. The interest in the liquid phase of light molecular compounds also largely stems from their geophysical and astrophysical relevance.

Our activity on simple molecular fluids under extreme P-T conditions has seen a strong development in the last years. First, in the framework of the ANR project MOFLEX (PI: F. Datchi), in collaboration with CEA and ESRF, a large effort has been put into developing innovative techniques for structural and vibrational measurements under extreme P-T. The latter, added to the future upgrade of ESRF-ID27, allow us to foresee a rich experimental program in the next years. Second, in the framework of the International ANR project PAX (PI: L.E. Bove), in collaboration with the Innsbruck University, and the ILL long-term project, the development of the quasi-elastic neutron scattering technique at high pressures (HP-QENS patent) has opened new access to the diffusive and tunnelling dynamics of the proton in hydrogenate systems at high P-T. This represents an important outcome for the international neutron community, in particular in view of the incoming operation of the European spallation source.

4.    Magnetism and thermal transport in simple oxides

Simple oxides are systems that present an important fundamental and technological interest for their large variety of magnetic, electrical and thermal behaviors and member of PHYSIX have a longstanding interest in these systems.  Our current projects  concern the magnetism under pressure of 3d-oxydes (FeO, MgO, Fe3O4), studied by neutron scattering in collaboration with Tokyo university; the combined experimental and theoretical study of phonon dynamics and thermal transport in simple materials such as (Mg,Fe)O-ferropericlase, SiO2-stishovite, and (Mg,Fe)SiO3-perovskite to understand the the microscopic mechanisms responsible for the thermal transport in simple insulating oxides.

5.    New theoretical approaches to kinetics and application to prebiotic chemistry

Starting from our recently developed powerful framework for the simulation of the transformations of matter, including complex poly(a)morphic phase transitions (see “Faits marquants”), already under application to a panel of materials, in the coming years we will focus on the invention of new approaches to kinetics. In fact, despite the widely acknowledged importance of the “thermodynamics vs kinetics” competition in experimentally accessible systems, the kinetic theory of transformations is way behind the corresponding free energy landscape theory. Building upon our original topological tools to analyze changes in inter-atomic networks, we will address the challenge of directly extracting kinetic rates from molecular dynamics trajectories – exploiting high performance computing facilities – without passing through over-simplified models built upon transition state theory. The new techniques, already under study, will be highly beneficial also for the study of activated processes in liquid phase, including nucleation of crystals and prebiotic chemical reactions at hydrothermal conditions, as well as in the study of the physics of molecular systems and materials under extreme conditions, including the possibility of designing novel synthetic routes. Our research program will foster collaborations within IMPMC, and outside of it with world leaders in these fields, and will also lead to the delivery of software tools to the scientific community.