UltraHighPressure

Ultrahigh pressure refers to pressures beyond those typically produced in routine high‑pressure experiments and encountered in planetary interiors or generated in specialized laboratories. In many contexts it means around or above 2 gigapascals (GPa), with experiments and natural rocks reaching hundreds of GPa. In geology and geophysics, ultrahigh‑pressure metamorphism denotes pressures greater than about 2–3 GPa, corresponding to depths roughly 60–100 kilometers or more. In physics and planetary science, ultrahigh pressures cover regimes where new phase transitions, unusual bonding, and exotic states of matter may occur, including proposals of metallic or superconducting phases.

In geology, ultrahigh‑pressure metamorphic rocks form during subduction to mantle depths and are later exhumed to the surface. Indicators include high‑pressure mineral assemblages such as coesite and diamond, which record rapid transport from deep to shallow environments and constrain pressures, temperatures, and timescales of subduction zones.

In the laboratory, ultrahigh pressure is generated with several approaches. The diamond anvil cell (DAC) static technique can reach well over 100 GPa and has approached several hundred GPa under certain conditions, enabling spectroscopy and diffraction studies in extreme environments. Multi‑anvil presses extend stable static compression to about 25–30 GPa with high temperatures. Dynamic methods, such as laser‑driven shocks or pulsed‑power techniques, can achieve hundreds of GPa for very short durations, useful for studying fast‑proceeding phase transitions.

Applications include investigating phase transitions of ice and hydrogen, high‑pressure forms of carbon, silicates, and other materials, with implications for planetary interiors and the search for novel, potentially useful materials. Challenges remain in maintaining and measuring stable conditions, scaling samples, and interpreting data at extreme pressures.