Under pressure, carbon dioxide mimics glass

Carbon, a multitalented element, has yet another trick to boast of. Researchers at the European Laboratory for Nonlinear Spectroscopy and the National Institute for the Physics of Matter, both in Italy, have coaxed carbon dioxide into forming glass at room temperature and high pressures (Nature 2006, 441, 857). In the newly synthesized solid, dubbed amorphous carbonia, or a-carbonia, the molecules form a three-dimensional interconnected network, similar to silica glass. The substance is very different from CO₂'s solid-phase cousin, dry ice, in which the molecules stay close together but remain separate. Earlier thermodynamics simulations by other scientists showed that such a phase could be metastable, but Mario Santoro, Federico Gorelli, and colleagues are the first to synthesize it. To prepare the glass, they compressed carbon dioxide molecules in a diamond anvil cell at pressures of 40 to 76 gigapascal, yielding a stable, stiff solid. This research may illuminate natural phenomena where CO₂ is pressurized, such as ice-covered planets and asteroids, and help develop new supercritical CO₂ solvents, the team suggests.