The pressure range in the universe spans more than 60 orders of magni-tude from the remotest vacuum of space to the centers of neutron stars. 105

Pressure causes dramatic changes in the behaviors of materials. It converts common liquids into spectacular crystals and turns common gases into exotic metals by the dramatic modification of interatomic distances and bond angles. Pressure provides an extremely powerful means of probing the relationship between structure and properties, which is necessary for a better fundamental understanding of the underlying phenomena and also for the improved design of materials [1]. In crystals, the most dramatic effects of pressure are phase transitions, which result in new polymorphs or different chemical species. The new crystal structures, sometimes with unusual stoichiometries, may present unexpected chemical and physical properties. For example, some chemical elements become superconductors under pressure [2] and simple metals such as lithium and sodium [3, 4], transform into insulators.