science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...

and

engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad range of more speciali ...

the study of high pressure examines its effects on materials and the design and construction of devices, such as a

diamond anvil cell A diamond anvil cell (DAC) is a high-pressure device used in geology, engineering, and materials science experiments. It enables the compression of a small (sub-millimeter-sized) piece of material to extreme pressures, typically up to around 1 ...

, which can create high

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

. By ''high pressure'' is usually meant pressures of thousands (kilo bars) or millions (megabars) of times

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...

(about 1 bar or 100,000 Pa).

History and overview

Percy Williams Bridgman Percy Williams Bridgman (April 21, 1882 – August 20, 1961) was an American physicist who received the 1946 Nobel Prize in Physics for his work on the physics of high pressures. He also wrote extensively on the scientific method and on other as ...

received a

Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...

in 1946 for advancing this area of physics by several magnitudes of pressure (400 MPa to 40,000 MPa). The list of founding fathers of this field includes also the names of Harry George Drickamer,

Tracy Hall Howard Tracy Hall (October 20, 1919 – July 25, 2008) was an American physical chemist and one of the early pioneers in the research of synthetic diamonds, using a press of his own design. Early life Howard Tracy Hall was born in Ogden, Uta ...

, Francis P. Bundy, Leonid F. Vereschagin, and Sergey M. Stishov. It was by applying high pressure as well as high

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

that man-made

diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, ...

s were first produced as well as many other interesting discoveries. Almost any material when subjected to high pressure will compact itself into a denser form, for example,

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

, also called

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

will first adopt a denser form known as

coesite Coesite is a form ( polymorph) of silicon dioxide Si O2 that is formed when very high pressure (2–3 gigapascals), and moderately high temperature (), are applied to quartz. Coesite was first synthesized by Loring Coes Jr., a chemist at the ...

, then upon application of even higher pressure, form stishovite. These two forms of silica were first discovered by high-pressure experimenters, but then found in nature at the site of a meteor impact. Chemical bonding is likely to change under high pressure, when the P*V term in the free energy becomes comparable to the energies of typical chemical bonds – i.e. at around 100 GPa. Among the most striking changes are metallization of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

at 96 GPa (rendering oxygen a superconductor), and transition of

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

from a nearly-free-electron metal to a transparent insulator at ~200 GPa. At ultimately high compression, however, all materials will metallize. High-pressure experimentation has led to the discovery of the types of minerals which are believed to exist in the deep mantle of the Earth, such as

silicate perovskite Silicate perovskite is either (the magnesium end-member is called bridgmanite) or ( calcium silicate known as davemaoite) when arranged in a perovskite structure. Silicate perovskites are not stable at Earth's surface, and mainly exist in the l ...

, which is thought to make up half of the Earth's bulk, and

post-perovskite Post-perovskite (pPv) is a high-pressure phase of magnesium silicate (MgSiO3). It is composed of the prime oxide constituents of the Earth's rocky mantle (MgO and SiO2), and its pressure and temperature for stability imply that it is likely to occur ...

, which occurs at the core-mantle boundary and explains many anomalies inferred for that region. Pressure "landmarks": typical pressures reached by large-volume presses are up to 30–40 GPa, pressures that can be generated inside

s are ~1000 GPa, pressure in the center of the Earth is 364 GPa, and highest pressures ever achieved in shock waves are over 100,000 GPa.

History and overview

See also

References

Further reading