The pressure range accessible to laboratory experiments exceeds now a remarkable 20 orders of magnitude, from ultra-high vacuum (< 1 nPa) to ultra-high pressures (> 100 GPa). With the development of high-pressure diamond-anvil cells we are now able to study materials at pressures equivalent to the pressure at the centre of our earth (350 GPa). In other planets and stars pressures beyond the TPa range are reached, which can only be explored by thermonuclear explosions or by theoretical methods. At high pressures unusual structures and materials properties are observed. It is currently a formidable task to obtain the equation-of-state for a solid up to high pressures and temperatures. Our research group has just achieved that recently for neon, where the isotherms are in excellent agreement with experimental data. Fundamental questions we are currently exploring is, for example, if we can already understand the simple density-pressure relationship of simple atomic crystals (like helium or neon) from squeezing atoms. We further present density functional results for the metallic phase transition of CrCl2 (see picture below) currently investigated experimentally at the Max-Planck Institute in Stuttgart, and for optical properties of ice.
Université Paul Sabatier - Bat. 3R1b4 - 118 route de Narbonne 31062 Toulouse Cedex 09, France