What is a Diamond Anvil Cell?

The diamond anvil cell is a machine used by physicists to put samples under extremely high pressures (up to ~360 gigapascals) for the purpose of researching their properties, including phase transitions, atomic bonding, viscosity and diffraction levels, and crystallographic structure. Diamond anvil cells can simulate pressures of millions of atmospheres, recreating conditions similar to those at the center of the Earth or inside the gas giants. They are among the only laboratory apparatus capable of creating forms of degenerate matter like metallic hydrogen.

Diamond anvil cells work on a simple principle -- by exerting a large amount of force on a small amount of area, tremendous net pressure may be obtained. The diamond anvil, successor to anvils made of carbon-tungsten alloy, was invented by researchers Weir, Lippincott, Van Valkenburg, and Bunting in the late 1950s as part of their work at the National Bureau of Standards (NBS). In addition to being the hardest material available at the time and virtually incompressible, the diamond is transparent, making it easy to view experimental samples as they are being compressed. It also helps in conducting spectroscopic experiments.

Three main components make up the diamond anvil cell. First are two flawless diamonds, with a weight of 1/8 to 1/3 carats, with parallel faces opposing each other. The culet, the place where the two diamonds make contact, usually has a diameter of about 0.6 mm. For experiments that require even higher pressures, the culet can be made even smaller.

The second component of the diamond anvil cell is a force-exerting device, pressing the diamonds against each other from both sides. These can be screws that tighten, gas pressing against a membrane, or a simple lever arm. The third component of the diamond anvil is a metallic gasket that encircles the perimeter of the culet, containing the sample and providing resistance to compression on the edges, lessening the possibility of anvil failure.

The diamond anvil cell is an important piece of equipment that allows us to simulate pressures that we would otherwise never see, giving us access to a world of materials that would otherwise be unobservable.