High-pressure chemistry

High-pressure chemistry studies how compression changes chemical bonding, crystal structures, and reactions. It examines materials under pressures far above ordinary atmospheric conditions.

Pressure-induced phase transition: A change in a material’s structure or state caused by increasing pressure. Compression can stabilize a different arrangement of atoms or molecules.
Diamond anvil cell: A device that compresses a tiny sample between the tips of two opposed diamonds. It generates extreme static pressures while leaving the sample accessible to probes.
Superhydride: A hydrogen-rich compound containing more hydrogen than conventional hydrides of its constituent element. Several superhydrides become superconducting only under extreme compression.
Static compression: The sustained compression of a sample using a pressure-generating apparatus. It permits prolonged measurements, unlike the brief pressure pulse of shock experiments.
Metallic hydrogen: A predicted conducting phase of hydrogen in which electrons behave as in a metal. Its production and properties remain central challenges in compressed-matter research.
Chemical bonding under pressure: Changes in bond lengths, strengths, and electronic character caused by compression. Pressure can alter which bonds are energetically favored and how atoms share electrons.
Shock compression: The rapid compression of matter by a propagating shock wave. It reaches pressures and temperatures on timescales inaccessible to static compression.
High-pressure ice: A family of crystalline and molecular ice phases stable at elevated pressures. Its many structures show how compression reorganizes hydrogen bonding and oxygen lattices.
Dynamic compression: The rapid compression of matter using a shock or other transient force. It reaches extreme conditions briefly, contrasting with maintained static pressure.
Room-temperature superconductivity: Superconductivity that persists near ordinary ambient temperatures. High-pressure hydrides have prompted claims and tests of superconductivity at unusually high temperatures.

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