X-ray crystallography of simple molecular solids up to mega-bar pressures: application to solid oxygen and carbon dioxide

A review of recently developed methods to study the structural properties of simple molecular solids under pressures up to the mega-bar range using synchrotron X-ray diffraction techniques is presented. This includes the growth of single-crystals at high pressure and temperature conditions and the use of He as pressure transmitting medium. The application of these methods to solid O₂ and CO₂ is then presented as illustrative examples, showing how they enabled to solve long-standing debates on the structure of the high-pressure crystalline phases of these compounds. (authors)