High Pressure Physics, Chemistry and Materials Science
This area deals with studies on matter under extreme pressures, up to several millions of atmospheres, and temperatures of 10-6000 K. In these conditions, our traditional view of the periodic table of elements is severely challenged, along with the high-school partition of solids into four classes: covalent, metallic, ionic, and molecular solids. For instance, insulating, covalent solids can be transformed into metals and even superconductors, and vice versa. Novel compounds are then obtained, which are superconductors at nearly room temperature, and the “sacred Graal” is the possible achievement of superconducting hydrogen. High pressures are obtained by squeezing matter between two opposed diamond anvils, in the diamond anvil cell. This cell is coupled to materials characterization techniques such as optical spectroscopy, and synchrotron X-ray diffraction and spectroscopy. In the last decade, our research has been achieving several remarkable findings. We discovered the high pressure transformation of solid molecular CO2 into a hard covalent solid similar to quartz (1), and also the existence of partially ionic, silica/non-molecular CO2 compounds (2). We then discovered an entire class of hybrid materials, with potential technological applications, made of guest polymers self-assembled at high pressure in host micro-porous crystals, the zeolite (3-6). Then, studies on the supercritical state of fluids, always thought to be a single phase system, revealed the existence of distinct gas-like and dense liquid-like regimes, which leads to a deeper understanding of thermodynamics (7,8). Finally, simple elemental liquids have been transformed to complex liquids, which shed a new light on liquid matter physics (9). In the future, we aim to discover novel polymer/zeolite materials with tailored technological properties. Since pressures are not very high in this case (several tens of thousands of atm. or even less), this synthesis could be easily extended to large volume (1 cm3) cells, which would open the realm of industrial applications. Also, we will synthesize at high pressures a variety of carbon based new materials, made of bundles of 1D nano-threads, a field which would also open highways for novel technologies. Finally, we will investigate the phase diagram of simple substances with the aim of obtaining exotic amorphous states of these systems, exhibiting high energy storage capability.