Under extreme pressures (400,000 to 500,000 atmospheres which is 40-50 gigapascals) the researchers found that CO2 forms a crystalline solid, dubbed "amorphous carbonia" (a-CO2). At present a-CO2 cannot exist outside of a pressure chamber as it reverts to normal CO2 with decompression. If it can somehow be made to remain solid under normal conditions, however, experts predict amorphous carbonia could have a range of applications. It could lead to a new, less environmentally harmful ways to dispose of CO2. The material's unusual optical properties could be useful in a laser.
Carbon nanotubes can be made to collapse with a force of 40 gigapascals when bombarded with electrons. This seems like an efficient way to produce a-CO2. We still need to determine how to keep them solid.